Dr Paul Stevenson MA (Oxon) MSc DPhil MInstP


Reader, Head of the Theoretical Nuclear Physics Group, Senior Personal Tutor
MA (Oxon) MSc (Open) DPhil (Oxon)

About

Areas of specialism

Nuclear Physics; Theoretical Physics; Computational Physics; Quantum Computing

University roles and responsibilities

  • Head of Nuclear Theory Group
  • Physics Senior Personal Tutor
  • Panel chair for University course validation

    My qualifications

    1999
    D.Phil, Nuclear Physics
    University of Oxford

    Research

    Research interests

    Supervision

    Postgraduate research supervision

    Teaching

    Publications

    Highlights

    "Low-Energy Heavy-Ion Reactions and Effective Forces", P. D. Stevenson and M. C. Barton, Prog. Part. Nucl. Phys. 104, 142 (2019) [ open access journal download | arxiv download (1809.05801) | surrey epubs download ]

    "Two-body dissipation effect in nuclear fusion reactions", Kai Wen, M. C. Barton, Arnau Rios Huguet, and P. D. Stevenson, Phys. Rev. C 98, 014603 (2018) [ journal download | arxiv download (1805.08152) | surrey epubs download ]

    "The Skyrme tensor force in heavy ion collisions", P. D. Stevenson, E. B. Suckling, S. Fracasso, M. C. Barton and A. S. Umar, Phys. Rev. C 93, 054617 (2016) [ journal download | arxiv download (1507.00645) | surrey epubs download ]

    "The TDHF Code Sky3D", J. A. Maruhn, P.-G. Reinhard, P. D. Stevenson and A. S. Umar, Comput. Phys. Commun. 185, 2195 (2014) [ open access journal download | arxiv download (1310.5946) | surrey epubs download ]

    Isaac Hobday, PAUL DENIS STEVENSON, JAMES BENSTEAD (2022)Quantum computing calculations for nuclear structure and nuclear data

    Calculations of nuclear properties and nuclear models are performed using quantum computing algorithms on simulated and real quantum computers. The models are a realistic calculation of deuteron binding based on effective field theory, and a simplified two-level version of the nuclear shell model. A method of reducing the number of qubits needed for practical calculation is presented, the reduction being with respect to that used when the standard Jordan-Wigner encoding is used. Its efficacy is shown in the case of the deuteron binding and shell model. A version of the variational quantum eigensolver in which all eigenstates in a spectrum are targeted on an equal basis is shown. The method involves finding the minima of the variance of the Hamiltonian, and its ability to find the full spectrum of small version of the simplified shell model is presented.

    JC Pei, FR Xu, PD Stevenson (2006)Deformation effects on the structures of N=7 halo nuclei, In: NUCLEAR PHYSICS A765(1-2)pp. 29-38 ELSEVIER SCIENCE BV
    PJR Mason, Zsolt Podolyak, N Marginean, Patrick Regan, Paul Stevenson, V Werner, T Alexander, A Algora, T Alharbi, M Bowry, R Britton, AM Bruce, D Bucurescu, M Bunce, G Cata-Danil, I Cata-Danil, N Cooper, D Deleanu, D Delion, D Filipescu, William Gelletly, D Ghita, I Gheorghe, T Glodariu, G Ilie, D Ivanova, S Kisyov, S Lalkovski, R Lica, SN Liddick, R Marginean, C Mihai, K Mulholland, CR Nita, A Negret, S Pascu, S Rice, OJ Roberts, T Sava, JF Smith, P-A Soederstroem, L Stroe, G Suliman, R Suvaila, S Toma, C Townsley, E Wilson, Rachael Wood, M Zhekova, C Zhou (2013)Half-life of the yrast 2(+) state in W-188: Evolution of deformation and collectivity in neutron-rich tungsten isotopes, In: PHYSICAL REVIEW C88(4)044301pp. ?-? AMER PHYSICAL SOC

    The half-life of the yrast I π = 2+ state in the neutron-rich nucleus 188W has been measured using fast-timing techniques with the HPGe and LaBr3:Ce array at the National Institute of Physics and Nuclear Engineering, Bucharest. The resulting value of t1/2 = 0.87(12) ns is equivalent to a reduced transition probability of B(E2; 2+ 1 → 0+ 1 ) = 85(12) W.u. for this transition. The B(E2; 2+ 1 → 0+ 1 ) is compared to neighboring tungsten isotopes and nuclei in the Hf, Os, and Pt isotopic chains. Woods-Saxon potential energy surface (PES) calculations have been performed for nuclei in the tungsten isotopic chain and predict prolate deformed minima with rapidly increasing γ softness for 184–192W and an oblate minimum for 194W.

    PD Stevenson, JMA Broomfield (2010)Testing a variational method for fluctuations, In: Journal of Physics: Conference Series205
    DT Joss, IG Darby, RD Page, J Uusitalo, S Eeckhaudt, T Grahn, PT Greenlees, PM Jones, R Julin, S Juutinen, S Ketelhut, M Leino, A-P Leppanen, M Nyman, J Pakarinen, P Rahkila, J Saren, C Scholey, A Steer, AJ Cannon, PD Stevenson, JS Al-Khalili, S Erturk, M Venhart, B Gall, B Hadinia, J Simpson (2006)Probing the limit of nuclear existence: Proton emission from Re-159, In: PHYSICS LETTERS B641(1)pp. 34-37 ELSEVIER SCIENCE BV
    P. D. Stevenson, M. P. Brine, Zs. Podolyak, P. H. Regan, P. M. Walker, J. Rikovska Stone (2005)Shape evolution in the neutron-rich tungsten region, In: Physical Review C72(047303)
    T Grahn, S Stolze, JT Joss, RD Page, B Saygi, D O'Donnell, M Akmali, K Andgren, L Bianco, DM Cullen, A Dewald, PT Greenlees, K Heyde, H Iwasaki, U Jakobsson, P Jones, DS Judson, R Julin, S Juutinen, S Ketelhut, M Leino, N Lumley, PJR Mason, O Moller, K Nomura, M Nyman, A Petts, P Peura, N Pietralla, T Pissulla, P Rahkila, PJ Sapple, J Saren, C Scholey, J Simpson, J Sorri, PD Stevenson, J Uusitalo, HV Watkins, JL Wood (2016)Excited states and reduced transition probabilities in 168Os, In: Physical Review C: Nuclear Physics94(4)

    The level scheme of the neutron-deficient nuclide 168Os has been extended and mean lifetimes of excited states have been measured by the recoil distance Doppler-shift method using the JUROGAM ____gamma-ray spectrometer in conjunction with the IKP K'oln plunger device. The 168Os ____gamma rays were measured in delayed coincidence with recoiling fusion-evaporation residues detected at the focal plane of the RITU gas-filled separator. The ratio of reduced transition probabilities B(E2;4_1^+ ____rightarrow 2_1^+)/B(E2;2_1^+ ____rightarrow 0_1^+) is measured to be 0.34(18), which is very unusual for collective band structures and cannot be reproduced by IBM-2 model calculations based on the SkM* energy-density functional.

    PD Stevenson, J Rikovska Stone, JC Miller, R Koncewicz, MR Strayer (2003)Nuclear matter and neutron star properties calculated with the Skyrme interaction, In: Phys. Rev. C68034324

    The effective Skyrme interaction has been used extensively in mean-field models for several decades and many different parametrizations of the interaction have been proposed. All of these give similar agreement with the experimental observables of nuclear ground states as well as with the properties of infinite symmetric nuclear matter at the saturation density n0. However, when applied over a wider range of densities (up to ∼3n0) they predict widely varying behavior for the observables of both symmetric and asymmetric nuclear matter. A particularly relevant example of naturally occurring asymmetric nuclear matter is the material of which neutron stars are composed. At around nuclear matter density, this can be well represented as a mixture of neutrons, protons, electrons, and muons (n+p+e+μ matter) in β-equilibrium, and these densities turn out to be the key ones for determining the properties of neutron-star models with masses near to the widely used “canonical” value of 1.4M⊙. By constructing equations of state for neutron-star matter using the different Skyrme parametrizations, calculating corresponding neutron-star models and then comparing these with observational data, an additional constraint can be obtained for the values of the Skyrme parameters. Such a constraint is particularly relevant because the parametrizations are initially determined by fitting to the properties of doubly closed-shell nuclei and it is an open question how suitable they then are for nuclei with high values of isospin, such as those at the neutron drip-line and beyond. The neutron-star environment provides an invaluable testing ground for this. We have carried out an investigation of 87 different Skyrme parametrizations in order to examine how successful they are in predicting the expected properties of infinite nuclear matter and generating plausible neutron-star models. This is the first systematic study of the predictions of the various Skyrme parametrizations for the density dependence of the characteristic observables of nuclear matter; the density dependence of the symmetry energy for β-equilibrium matter turns out to be a crucial property for indicating which Skyrme parameter sets will apply equally well for finite nuclei and for neutron-star matter. Only 27 of the 87 parametrizations investigated pass the test of giving satisfactory neutron-star models and we present a list of these.

    J. N. Orce, A. M. Bruce, A. Emmanouilidis, A. P. Byrne, G. D. Dracoulis, T. Kibédi, M. Caamano, H. El-Masri, C. J. Pearson, Zs. Podolyák, P. D. Stevenson, P. M. Walker, F. R. Xu, D. M. Cullen, C. Wheldon (2006)Shape-driving effects in the triaxial nucleus, 128Xe, In: Physical Review C74(034318)
    J C Pei, F R Xu, P D Stevenson (2005)Density Distributions of Superheavy Nuclei, In: Physical Review C71(3)

    We employed the Skyrme-Hartree-Fock model to investigate the density distributions and their dependence on nuclear shapes and isospins in the superheavy mass region. Different Skyrme forces were used for the calculations with a special comparison to the experimental data in Pb-208. The ground-state deformations, nuclear radii, neutron-skin thicknesses and alpha-decay energies were also calculated. Density distributions were discussed with the calculations of single-particle wave functions and shell fillings. Calculations show that deformations have considerable effects on the density distributions, with a detailed discussion on the (292)120 nucleus. Earlier predictions of remarkably low central density are not supported when deformation is allowed for.

    PD Stevenson, PM Goddard, JR Stone, M Dutra (2013)Do Skyrme forces that fit nuclear matter work well in finite nuclei?, In: XXXV BRAZILIAN WORKSHOP ON NUCLEAR PHYSICS1529pp. 262-268
    T. Shizuma, P. D. Stevenson, P. M. Walker, Y. Toh, T. Hayakawa, M. Oshima, K. Furuno, T. Komatsubar (2002)High-K negative parity states in 184Os, In: Physical Review C65(064310)
    JA Maruhn, P-G Reinhard, PD Stevenson, MR Strayer (2006)Spin-excitation mechanisms in Skyrme-force time-dependent Hartree-Fock calculations, In: PHYSICAL REVIEW C74(2)ARTN 0pp. ?-? AMERICAN PHYSICAL SOC
    G A Jones, P H Regan, P M Walker, Z Podolyak, P D Stevenson, M P Carpenter, J J Carroll, R S Chakrawarthy, P Chowdhury, A B Garnsworthy, R V Janssens, T L Khoo, F G Kondev, G J Lane, Z Liu, D Seweryniak, N J Thompson, S Zhu, S J Williams (2007)Identification of a High-Spin Isomer in Mo-99, In: Physical Review C76(4)

    A previously unreported isomer has been identified in Mo-99 at an excitation energy of E-x = 3010 keV, decaying with a half-life of T-1/2 = 8(2) ns. The nucleus of interest was produced following fusion-fission reactions between a thick Al-27 target frame and a Hf-178 beam at a laboratory energy of 1150 MeV. This isomeric state is interpreted as an energetically favored, maximally aligned configuration of nu h (11/2) circle times pi(g (9/2))(2).

    Kai Wen, M. C. Barton, Arnau Rios, P. D. Stevenson (2018)Two-body dissipation effect in nuclear fusion reactions, In: Physical Review C98(1)014603pp. 014603-1 American Physical Society

    Friction coefficients for the fusion reaction 16O+16O → 32S are extracted based on both the time-dependent Hartree-Fock and the time-dependent density matrix methods. The latter goes beyond the mean-field approximation by taking into account the effect of two-body correlations, but in practical simulations of fusion reactions we find that the total energy is not conserved. We analyze this problem and propose a solution that allows for a clear quantification of dissipative effects in the dynamics. Compared to mean-field simulations, friction coefficients in the density-matrix approach are enhanced by about 20 %. An energy-dependence of the dissipative mechanism is also demonstrated, indicating that two-body collisions are more efficient at generating friction at low incident energies.

    PD Stevenson (2002)Analytic angular momentum coupling coefficient calculators, In: COMPUTER PHYSICS COMMUNICATIONS147(3)PII S0010-pp. 853-858 ELSEVIER SCIENCE BV
    FR Xu, JC Pei, PD Stevenson (2006)Deformed halo nuclei in mean-field approach, In: AIP Conference Proceedings865pp. 96-100

    The halo properties of the odd light nuclei have been studied with the deformed Skyrme-Hartree-Fock model, in which the blocking effect of the odd nucleon is taken into account. For nuclei near drip lines, the pairing was treated in the frame of Lipkin-Nogami method, using a volume-surface mixing paring interaction. The 1/2+ state in 11Be was calculated to have a very large soft deformation. The origin of deformed halo structures was discussed. © 2006 American Institute of Physics.

    K. Wen, M.C. Barton, A. Rios, P.D. Stevenson (2019)Dissipation Dynamics of Nuclear Fusion Reactions, In: Acta Physica Polonica B - proceedings of the 2018 Zakopane Conference on Nuclear Physics Extremes of the Nuclear Landscape50(3)pp. 567-572 Jagiellonian University

    Based on both the time-dependent Hartree–Fock (TDHF) and the time-dependent density matrix (TDDM) methods, we adopt a macroscopic reduction procedure to investigate the dissipation dynamics of nuclear fusion reactions. The TDDM method is an extension of TDHF, in the sense that it goes beyond the mean-field concept and takes into account two-body correlations explicitly. To investigate the effect of correlations on dissipation, the collective trajectories as well as the friction coefficients for the reaction ¹⁶O + ¹⁶O →³²S are extracted. Our results suggest that two-body correlations play a relevant role in the fusion process.

    EB Suckling, PD Stevenson (2010)The effect of the tensor force on the predicted stability of superheavy nuclei, In: EPL90(1)ARTN 1pp. ?-? EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY
    P Regan, P Stevenson (2005)Preface - NUSTAR 2005, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS31(10) IOP PUBLISHING LTD
    M Oi, PH Regan, FR Xu, PM Walker, AK Rath, PD Stevenson (2002)Cranked-Hartree-Fock-Bogoliubov analysis at the valence maximum: Yrast behaviour of Dy-170(66)104, In: PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT(146)pp. 609-610
    P D Stevenson, M P Brine, Z Podolyak, P H Regan, P M Walker, J R Stone (2005)Shape Evolution in the Neutron-Rich Tungsten Region, In: Physical Review C72(4)

    Recent experimental data on the low-lying states in W-190 show a change in the E(4(1)(+))/E(2(1)(+)) behavior compared to less neutron-rich neigbors. Self-consistent axially-deformed Hartree-Fock calculations, using a separable monopole interaction, of nuclei in the vicinity of W-190 are performed to systematically examine the evolution of ground state quadrupole deformations. It is found that the neutron number N=116 causes a coexistence of oblate and prolate shapes, with a weak dependence on proton number, thereby hindering the development of these isotones as well-deformed rotors.

    RK Gupta, SK Patra, PD Stevenson, W Greiner (2007)A highly neutron-rich cluster and/or a superheavy nucleus in the compound nucleus U-238+U-238: A mean field study, In: INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS16(6)pp. 1721-1732 WORLD SCIENTIFIC PUBL CO PTE LTD
    RD Page, L Bianco, IG Darby, DT Joss, J Simpson, JS Al-Khalili, AJ Cannon, RJ Cooper, S Eeckhaudt, S Erturk, B Gall, T Grahn, PT Greenlees, B Hadinia, PM Jones, DS Judson, R Julin, S Juutinen, S Ketelhut, M Labiche, M Leino, A-P Leppanen, M Nyman, D O'Donnell, P Rahkila, PJ Sapple, J Saren, C Scholey, AN Steer, PD Stevenson, EB Suckling, J Thomson, J Uusitalo, M Venhart (2008)Decays of New Nuclides and Isomers Beyond the Proton Drip Line - The Influence of Neutron Configurations, In: I Boztosun, AB Balantekin (eds.), NUCLEAR PHYSICS AND ASTROPHYSICS1072pp. 172-178
    D Almehed, PD Stevenson (2005)Isovector giant monopole resonances in spherical nuclei, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS31(10)pp. S1819-S1822 IOP PUBLISHING LTD
    AN Antonov, MK Gaidarov, MV Ivanov, DN Kadrev, M Aïche, G Barreau, S Czajkowski, B Jurado, G Belier, A Chatillon, T Granier, J Taieb, D Doré, A Letourneau, D Ridikas, E Dupont, E Berthoumieux, S Panebianco, F Farget, C Schmitt, L Audouin, E Khan, L Tassan-Got, T Aumann, P Beller, K Boretzky, A Dolinskii, P Egelhof, H Emling, B Franzke, H Geissel, A Kelic-Heil, O Kester, N Kurz, Y Litvinov, G Münzenberg, F Nolden, K-H Schmidt, C Scheidenberger, H Simon, M Steck, H Weick, J Enders, N Pietralla, A Richter, G Schrieder, A Zilges, MO Distler, H Merkel, U Müller, AR Junghans, H Lenske, M Fujiwara, T Suda, S Kato, T Adachi, S Hamieh, MN Harakeh, N Kalantar-Nayestanaki, H Wörtche, GPA Berg, IA Koop, PV Logatchov, AV Otboev, VV Parkhomchuk, DN Shatilov, PY Shatunov, YM Shatunov, SV Shiyankov, DI Shvartz, AN Skrinsky, LV Chulkov, BV Danilin, AA Korsheninnikov, EA Kuzmin, AA Ogloblin, VA Volkov, Y Grishkin, VP Lisin, AN Mushkarenkov, V Nedorezov, AL Polonski, NV Rudnev, AA Turinge, A Artukh, V Avdeichikov, SN Ershov, A Fomichev, M Golovkov, AV Gorshkov, L Grigorenko, S Klygin, S Krupko, IN Meshkov, A Rodin, Y Sereda, I Seleznev, S Sidorchuk, E Syresin, S Stepantsov, G Ter-Akopian, Y Teterev, AN Vorontsov, SP Kamerdzhiev, EV Litvinova, S Karataglidis, R Alvarez Rodriguez, MJG Borge, C Fernandez Ramirez, E Garrido, P Sarriguren, JR Vignote, LM Fraile Prieto, J Lopez Herraiz, E Moya De Guerra, J Udias-Moinelo, JE Amaro Soriano, AM Lallena Rojo, JA Caballero, HT Johansson, B Jonson, T Nilsson, G Nyman, M Zhukov, P Golubev, D Rudolph, K Hencken, J Jourdan, B Krusche, T Rauscher, D Kiselev, D Trautmann, J Al-Khalili, W Catford, R Johnson, PD Stevenson, C Barton, D Jenkins, R Lemmon, M Chartier, D Cullen, CA Bertulani, A Heinz (2011)The electronion scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR) - A conceptual design study, In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment637(1)pp. 60-76
    MP Brine, PD Stevenson, JA Maruhn, P-G Reinhard (2006)Dipole response in neutron-rich magnesium, In: INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS15(7)pp. 1417-1423
    JA Maruhn, P-G Reinhard, Paul Stevenson, AS Umar (2014)The TDHF code Sky3D, In: Computer Physics Communications185(7)pp. 2195-2216 ELSEVIER SCIENCE BV

    The nuclear mean-field model based on Skyrme forces or related density functionals has found widespread application to the description of nuclear ground states, collective vibrational excitations, and heavy-ion collisions. The code Sky3D solves the static or dynamic equations on a three-dimensional Cartesian mesh with isolated or periodic boundary conditions and no further symmetry assumptions. Pairing can be included in the BCS approximation for the static case. The code is implemented with a view to allow easy modifications for including additional physics or special analysis of the results.

    PD Stevenson, JMA Broomfield (2009)A Variational Approach to Mass Fluctuations, In: M Milin, T Niksic, D Vretenar, S Szilner (eds.), NUCLEAR STRUCTURE AND DYNAMICS '091165pp. 177-180
    SK Patra, RK Gupta, BK Sharma, PD Stevenson, W Greiner (2007)Exotic clustering in heavy and superheavy nuclei within the relativistic and non-relativistic mean field formalisms, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS34(9)pp. 2073-2090 IOP PUBLISHING LTD
    Paul D. Stevenson, J.L Willerton (2019)A time-dependent Hartree-Fock study of triple-alpha dynamics, In: SciPost Physics Proceedings3

    Time-dependent Hartree-Fock calculations have been performed for fusion reactions of 4He + 4He → 8Be∗, followed by 4He + 8Be∗. Depending on the orientation of the initial state, a linear chain vibrational state or a triangular vibration is found in 12C, with transitions between these states observed. The vibrations of the linear chain state and the triangular state occur at '9 and 4 MeV respectively

    J N Orce, A M Bruce, A Emmanouilidis, A P Byrne, G D Dracoulis, T Kibedi, M Caamano, H El-Masri, C J Pearson, Z Podolyak, P D Stevenson, P M Walker, F R Xu, D M Cullen, C Wheldon (2006)Shape-Driving Effects in the Triaxial Nucleus, Xe-128, In: Physical Review C74(3)

    An extended decay scheme for Xe-128 has been constructed by using data from the Sn-124(Be-9, 5n)Xe-128 reaction at a beam energy of 58 MeV. Bands have been identified as being built on several intrinsic states, including a proposed 9/2(-)[514] circle times 1/2(+)[400] two-quasineutron configuration that forms the K-pi=5(-) intrinsic state at 2228 keV, and on a previously assigned K-pi=8(-) intrinsic state at 2786 keV. A half-life of 73(3) ns has been measured for the latter. Theoretical calculations have been performed by using the configuration-constrained blocking method based on a nonaxial Woods-Saxon potential. Large gamma deformation and gamma softness are predicted for the ground state and the K-pi=5(-) intrinsic state, whereas a nearly axially symmetric shape is predicted for the K-pi=8(-) two-quasiparticle configuration. The low value of the hindrance factor for the E1 transition depopulating the K-pi=8(-) intrinsic state is discussed in the context of analogous transitions in neighbouring N=74 isotones.

    GA Jones, PH Regan, PM Walker, Z Podolyak, PD Stevenson, MP Carpenter, JJ Carroll, RS Chakrawarthy, P Chowdhury, AB Garnsworthy, RVF Janssens, TL Khoo, FG Kondev, GJ Lane, Z Liu, D Seweryniak, NJ Thompson, S Zhu, SJ Williams (2007)Identification of a high-spin isomer in (99)Mo, In: PHYSICAL REVIEW C76(4)ARTN 0pp. ?-? AMER PHYSICAL SOC
    K Nomura, T Otsuka, R Rodriguez-Guzman, LM Robledo, P Sarriguren, PH Regan, PD Stevenson, Z Podolyak (2011)Spectroscopic calculations of the low-lying structure in exotic Os and W isotopes, In: PHYSICAL REVIEW C83(5)ARTN 0pp. ?-? AMER PHYSICAL SOC
    JS AI-Khaffli, AJ Cannon, PD Stevenson (2007)The two-potential approach to one-proton emission, In: LS Ferreira, P Arumugam (eds.), PROTON EMITTING NUCLEI AND RELATED TOPICS961pp. 66-71
    JMA Broomfield, PD Stevenson (2008)Mass dispersions from giant dipole resonances using the Balian-Veneroni variational approach, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS35(9)ARTN 0pp. ?-? IOP PUBLISHING LTD
    PM Goddard, PD Stevenson, A Rios, S Lunardi, PG Bizzeti, S Kabana, C Bucci, M Chiari, A Dainese, P DiNezza, R Menegazzo, A Nannini, C Signorini, JJ ValienteDobon (2014)Cause of the charge radius isotope shift at the N=126 shell gap, In: INPC 2013 - INTERNATIONAL NUCLEAR PHYSICS CONFERENCE, VOL. 166ARTN 0pp. ?-? E D P SCIENCES
    M. Pancic, Y. Qiang, J.C Pei, P.D Stevenson (2020)Shape evolutions in fission dynamics within time-dependent Hartree-Fock approach, In: Frontiers in Physics Frontiers Media

    We studied the nuclear shape evolutions in fission process of 240Pu by the time-dependent Hartree- Fock approach with various Skyrme forces. Calculations are performed for the later phase of the fission with large initial deformations towards the scission. We show that calculations with Skyrme forces with large surface energies and large symmetry energies can have extremely long fission evolution time. The symmetry energy plays a role in the evolution of neutron-rich necks. In addition, we also demonstrated the shape oscillations of fission fragments after the fission. We see that particularly the heavy near-spherical fragments have remarkable octupole oscillations.

    PD Stevenson, EB Suckling, S Fracasso, ED Simmons, AS Umar (2015)Role of the Skyrme tensor force in heavy-ion fusion, In: VI INTERNATIONAL CONFERENCE FUSION1486pp. ?-?

    We make use of the Skyrme e ff ective nuclear interaction within the time-dependent Hartree-Fock framework to assess the e ff ect of inclusion of the tensor terms of the Skyrme interaction on the fusion window of the 16 O– 16 O reaction. We find that the lower fusion threshold, around the barrier, is quite insensitive to these details of the force, but the higher threshold, above which the nuclei pass through each other, changes by several MeV between di ff erent tensor parametrisations. The results suggest that eventually fusion properties may become part of the evaluation or fitting process for e ff ective nuclear interactions

    PD Stevenson, D Almehed, P-G Reinhard, JA Maruhn (2007)Monopole Giant Resonances and TDHF boundary conditions, In: Nuclear Physics A788pp. 343-348 Elsevier
    P Goddard, P Stevenson, A Rios (2016)Fission dynamics within time-dependent Hartree-Fock. II. Boost-induced fission, In: PHYSICAL REVIEW C93(1)ARTN 01462 AMER PHYSICAL SOC

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus and the daughter products. Purpose: We explore the ability of dynamic mean-field methods to describe induced fission processes, using quadrupole boosts in the nuclide 240Pu as an example. Methods: Following upon the work presented in Goddard et al. [Phys. Rev. C 92, 054610 (2015)], quadrupoleconstrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simulation, with emphasis on fissioned final states. The corresponding fission fragment mass numbers are studied. Results: In general, the energy deposited by the quadrupole boost is quickly absorbed by the nucleus. In instantaneous boosts, this leads to fast shape rearrangements and violent dynamics that can ultimately lead to fission. This is a qualitatively different process than the deformation-induced fission. Boosts induced within a finite time window excite the system in a relatively gentler way and do induce fission but with a smaller energy deposition. Conclusions: The fission products obtained using boost-induced fission in time-dependent Hartree-Fock are more asymmetric than the fragments obtained in deformation-induced fission or the corresponding adiabatic approaches.

    A Rios Huguet, PD Stevenson, P Goddard (2015)Fission dynamics within time-dependent Hartree-Fock: Deformation-induced fission, In: Physical Review C: Nuclear Physics92054610 American Physical Society

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus and the daughter products. Purpose: We explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide 240Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate nonadiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behavior. Those beginning just beyond the barrier explore large-amplitude motion but do not fission, whereas those beginning beyond the two-fragment pathway crossing fission to final states which differ according to the exact initial deformation. Conclusions: Time-dependent Hartree-Fock is able to give a good qualitative and quantitative description of fast fission, provided one begins from a sufficiently deformed state.

    CI Pardi, PD Stevenson (2013)Continuum time-dependent Hartree-Fock method for giant resonances in spherical nuclei, In: Physical Review C - Nuclear Physics87(1) American Physical Society

    This paper deals with the solution of the spherically symmetric time-dependent Hartree-Fock approximation applied in the case of nuclear giant monopole resonances in the small and large amplitude regimes. The problem is spatially unbounded as the resonance state is in the continuum. The practical requirement to perform the calculation in a finite-sized spatial region results in a difficulty with the spatial boundary conditions. Here we propose an absorbing boundary condition scheme to handle the conflict. The derivation, via a Laplace transform method, and implementation is described. The accuracy and efficiency of the scheme is tested and the results presented to support the case that they are a effective way of handling the artificial boundary. © 2013 American Physical Society.

    PD Stevenson (2016)Resonances and reactions from mean-field dynamics, In: A Andreev, N Arsenyev, S Ershov, V Sargsyan, A Vdovin (eds.), INTERNATIONAL CONFERENCE ON NUCLEAR STRUCTURE AND RELATED TOPICS (NSRT15)107
    PD Stevenson, JR Stone, MR Strayer (2002)Mean field calculation of Ne, Mg and Si nuclei at N=20 with the separable monopole interaction, In: PHYSICS LETTERS B545(3-4)PII S0370-pp. 291-297 ELSEVIER SCIENCE BV
    BK Sharma, P Arumugam, SK Patra, PD Stevenson, RK Gupta, W Greiner (2006)Clustering in superheavy nuclei within the relativistic mean field approach, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS32(1)pp. L1-L9 IOP PUBLISHING LTD
    Mrutunjaya Bhuyan, Bhoomika Maheshwari, H A Kassim, N Yusoff, S K Patra, Brett V Carlson, PAUL DENIS STEVENSON (2021)The kinks in charge radii across N = 82 and 126 revisited, In: Journal of physics G, Nuclear and particle physics IOP Publishing

    We revisit the studies of the isotopic shift in the charge radii of even-even isotopes of Sn and Pb nuclei at N = 82, and 126, respectively, within the relativistic mean-field and Relativistic-Hartree-Bogoliubov approach. The shell model is also used to estimate isotopic shift in these nuclei, for the first time, to the best of our knowledge. The ground state single-particle energies (spe) are calculated for non-linear NL3 & NL3 * and density-dependent DD-ME2 parameter sets compared with the experimental data, wherever available. We establish a correlation between the filling of single-particle levels and the isotopic shift in occupation probabilities. The obtained spe from the relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches are in line with those used in the shell model and experimental data for both the Sn and Pb isotopic chains. The shell model calculated isotopic shift agrees with relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches that explain the experimental data quite well.

    N Al-Dahan, PH Regan, Z Podolyák, PM Walker, N Alkhomashi, GD Dracoulis, G Farrelly, J Benlliure, SB Pietri, RF Casten, PD Stevenson, W Gelletly, SJ Steer, AB Garnsworthy, E Casarejos, J Gerl, HJ Wollersheim, J Grebosz, M Górska, I Kojouharov, H Schaffner, A Algora, G Benzoni, A Blazhev, P Boutachkov, AM Bruce, IJ Cullen, AM Denis Bacelar, AY Deo, ME Estevez, Y Fujita, R Hoischen, R Kumar, S Lalkovski, Z Liu, PJ Mason, C Mihai, F Molina, D Mücher, B Rubio, A Tamii, S Tashenov, JJ Valiente-Dobón, PJ Woods (2012)Multiple β - Decaying states in 194Re: Shape evolution in neutron-rich osmium isotopes, In: Physical Review C - Nuclear Physics85(3)034301pp. ?-? American Physical Society

    decays from heavy, neutron-rich nuclei with A∼190 have been investigated following their production via the relativistic projectile fragmentation of an E/A=1 GeV 208Pb primary beam on a ∼2.5 g/cm2 9Be target. The reaction products were separated and identified using the GSI FRagment Separator (FRS) and stopped in the RISING active stopper. γ decays were observed and correlated with these secondary ions on an event-by-event basis such that γ-ray transitions following from both internal (isomeric) and β decays were recorded. A number of discrete, β-delayed γ-ray transitions associated with β decays from 194Re to excited states in 194Os have been observed, including previously reported decays from the yrast Iπ=(6+) state. Three previously unreported γ-ray transitions with energies 194, 349, and 554 keV are also identified; these transitions are associated with decays from higher spin states in 194Os. The results of these investigations are compared with theoretical predictions from Nilsson multi-quasiparticle (MQP) calculations. Based on lifetime measurements and the observed feeding pattern to states in 194Os, it is concluded that there are three β−-decaying states in 194Re.

    FR Xu, JC Pei, PD Stevenson (2005)Densities of superheavy nuclei at closed shells, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS31(10)pp. S1541-S1544 IOP PUBLISHING LTD
    P. M Walker, P. D Stevenson (2021)Configuration mixing and K -forbidden E2 decays, In: Physical Review C103(6)064305 American Physical Society

    Hindrance factors for K-forbidden E2 decays from multiquasiparticle isomers are analyzed in relation to mixing matrix elements that are often associated with chance near degeneracies, and a functional relationship is established. Focusing on effective matrix elements for ΔK=6 decays from three-quasiparticle isomers, significant configuration dependence is demonstrated.

    M Caamano, PM Walker, PH Regan, M Pfutzner, Z Podolyak, J Gerl, M Hellstrom, P Mayet, MN Mineva, A Aprahamian, J Benlliure, AM Bruce, PA Butler, DC Gil, DM Cullen, J Doring, T Enqvist, C Fox, JG Narro, H Geissel, W Gelletly, J Giovinazzo, M Gorska, H Grawe, R Grzywacz, A Kleinbohl, W Korten, M Lewitowicz, R Lucas, H Mach, CD O'Leary, F De Oliveira, CJ Pearson, F Rejmund, M Rejmund, M Sawicka, H Schaffner, C Schlegel, K Schmidt, KH Schmidt, PD Stevenson, C Theisen, F Vives, DD Warner, C Wheldon, HJ Wollersheim, S Wooding, F Xu, O Yordanov (2005)Isomers in neutron-rich A approximate to 190 nuclides from Pb-208 fragmentation, In: EUROPEAN PHYSICAL JOURNAL A23(2)pp. 201-215 SPRINGER
    JN Orce, AM Bruce, A Emmanouilidis, C Wheldon, FR Xu, PM Walker, M Caamano, Z Podolyak, H El-Masri, PD Stevenson, AP Byrne, GD Dracoulis, JC Hazel, T Kibedi, DM Cullen (2003)Interplay between K-isomerism and gamma-softness in Xe-128, In: ACTA PHYSICA POLONICA B34(4)pp. 2253-2256
    B. Schuetrumpf, P.-G. Reinhard, P.D. Stevenson, A.S. Umar, J.A. Maruhn (2018)The TDHF code Sky3D version 1.1, In: Computer Physics Communications229pp. 211-213 Elsevier

    The nuclear mean-field model based on Skyrme forces or related density functionals has found widespread application to the description of nuclear ground states, collective vibrational excitations, and heavy-ion collisions. The code Sky3D solves the static or dynamic equations on a three-dimensional Cartesian mesh with isolated or periodic boundary conditions and no further symmetry assumptions. Pairing can be included in the BCS approximation for the static case. The code is implemented with a view to allow easy modifications for including additional physics or special analysis of the results.

    M Centelles, SK Patra, X Roca-Maza, BK Sharma, PD Stevenson, X Vinas (2010)The influence of the symmetry energy on the giant monopole resonance of neutron-rich nuclei analyzed in Thomas-Fermi theory, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS37(7)ARTN 0pp. ?-? IOP PUBLISHING LTD
    CI Pardi, PD Stevenson, K Xu (2014)Extension of the continuum time-dependent Hartree-Fock method to proton states, In: PHYSICAL REVIEW E89(3)ARTN 0pp. ?-? AMER PHYSICAL SOC
    AD Godbeer, JS Al-Khalili, PD Stevenson (2015)Modelling proton tunnelling in the adenine-thymine base pair., In: Phys Chem Chem Phys17(19)pp. 13034-13044

    The energies of the canonical (standard, amino-keto) and tautomeric (non-standard, imino-enol) charge-neutral forms of the adenine-thymine base pair (A-T and A*-T*, respectively) are calculated using density functional theory. The reaction pathway is then computed using a transition state search to provide the asymmetric double-well potential minima along with the barrier height and shape, which are combined to create the potential energy surface using a polynomial fit. The influence of quantum tunnelling on proton transfer within a base pair H-bond (modelled as the DFT deduced double-well potential) is then investigated by solving the time-dependent master equation for the density matrix. The effect on a quantum system by its surrounding water molecules is explored via the inclusion of a dissipative Lindblad term in the master equation, in which the environment is modelled as a heat bath of harmonic oscillators. It is found that quantum tunnelling, due to transitions to higher energy eigenstates with significant amplitudes in the shallow (tautomeric) side of the potential, is unlikely to be a significant mechanism for the creation of adenine-thymine tautomers within DNA, with thermally assisted coupling of the environment only able to boost the tunnelling probability to a maximum of 2 × 10(-9). This is barely increased for different choices of the starting wave function or when the geometry of the potential energy surface is varied.

    RK Gupta, SK Patra, PD Stevenson, C Beck, W Greiner (2008)Fission of hyper-hyperdeformed Ni-56: a clustering analysis within mean-field approaches, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS35(7)ARTN 07510 IOP PUBLISHING LTD
    Paul Stevenson, Matthew Barton (2018)Low-Energy Heavy-Ion Reactions and the Skyrme Effective Interaction, In: Progress in Particle and Nuclear Physics104pp. 142-164 Elsevier

    The Skyrme effective interaction, with its multitude of parameterisations, along with its implementation using the static and time-dependent density functional (TDHF) formalism have allowed for a range of microscopic calculations of low-energy heavy-ion collisions. These calculations allow variation of the effective interaction along with an interpretation of the results of this variation informed by a comparison to experimental data. Initial progress in implementing TDHF for heavy-ion collisions necessarily used many approximations in the geometry or the interaction. Over the last decade or so, the implementations have overcome all restrictions, and studies have begun to be made where details of the effective interaction are being probed. This review surveys these studies in low energy heavy-ion reactions, finding significant effects on observables from the form of the spin-orbit interaction, the use of the tensor force, and the inclusion of time-odd terms in the density functional.

    PG Reinhard, PD Stevenson, D Almehed, JA Maruhn, MR Strayer (2006)Role of boundary conditions in dynamic studies of nuclear giant resonances and collisions, In: PHYSICAL REVIEW E73(3)ARTN 0pp. ?-? AMERICAN PHYSICAL SOC
    PJR Mason, Z Podolyak, NM Arginean, PH Regan, T Alexander, A Algora, T Alharbi, M Bowry, R Britton, D Bucurescu, AM Bruce, M Bunce, G Cata-Danil, I Cata-Danil, N Cooper, D Deleanu, D Delion, D Filipescu, W Gelletly, T Glodariu, I Gheorghe, D Ghita, G Ilie, D Ivanova, S Kisyov, S Lalkovski, R Lica, SN Liddick, R Marginean, C Mihai, K Mulholland, A Negret, CR Nita, S Rice, OJ Roberts, T Sava, JF Smith, P-A Soederstroem, PD Stevenson, L Stroe, S Toma, C Townsley, V Werner, E Wilson, RT Wood, NV Zamfir, M Zhekova, T Niksic, M Milin, D Vretenar, S Szilner (2012)Li-7-Induced Reactions for Fast-Timing With LaBr3:Ce Detectors, In: NUCLEAR STRUCTURE AND DYNAMICS '121491pp. 93-96
    RD Page, L Bianco, IG Darby, DT Joss, T Grahn, R-D Herzberg, J Pakarinen, J Thomson, J Uusitalo, S Eeckhaud, PT Greenlees, PM Jones, R Julin, S Juutinen, S Ketelhut, M Leino, A-P Leppanen, M Nyman, P Rahkila, J Saren, C Scholey, A Steer, M Venhart, J Simpson, JS Al-Khalili, AJ Cannon, PD Stevenson, S Erturk, B Gall, B Hadinia (2007)Probing single-particle structures beyond the proton drip line, In: LS Ferreira, P Arumugam (eds.), PROTON EMITTING NUCLEI AND RELATED TOPICS961pp. 137-142
    PD Stevenson, S Fracasso (2010)Extracting structure information from TDHF, In: J PHYS G NUCL PARTIC37(6)064030 IOP PUBLISHING LTD
    PD Stevenson, MR Strayer, JR Stone, WG Newton (2004)Giant resonances from TDHF, In: INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS13(1)pp. 181-185 WORLD SCIENTIFIC PUBL CO PTE LTD
    AD Godbeer, JS Al-Khalili, PD Stevenson (2014)Environment-induced dephasing versus von Neumann measurements in proton tunneling, In: PHYSICAL REVIEW A90(1)ARTN 0pp. ?-? AMER PHYSICAL SOC
    PD Stevenson, CI Pardi, S Lunardi, PG Bizzeti, S Kabana, C Bucci, M Chiari, A Dainese, P DiNezza, R Menegazzo, A Nannini, C Signorini, JJ ValienteDobon (2014)Isoscalar and Isovector Giant Monopole Resonances from a Continuum Hartree-Fock Method, In: INPC 2013 - INTERNATIONAL NUCLEAR PHYSICS CONFERENCE, VOL. 166ARTN 0pp. ?-? E D P SCIENCES
    P D Stevenson, P M Goddard (2012)Constraints on Skyrme Force Parameterizations, In: Proceedings of XXXI Rila Mountain Workshop

    Since its first use in Hartree-Fock calculations in 1972, the Skyrme Force, which includes around ten free parameters to be fitted to data, has un- dergone many such fitting procedures to different sets of data. To date there have been more than 200 parameter sets published. Since the Skyrme force can be thought of as an expansion of an in principle exact density functional, the Skyrme force has sufficient degrees of freedom that the different parameter sets can differ from each other quite extensively in how they reproduce the properties of nuclei. We give a selected history of the fitting of Skyrme forces, then ex- plore some recent work on systematically testing each parameterisation against experimentally-derived nuclear matter properties, and discuss the ability of the (few) parameter sets which pass all constraints to reproduce data in finite nuclei.

    PD Stevenson, A Rios, PM Goddard (2015)Shapes and Dynamics from the Time-Dependent Mean Field, In: Bulgarian Journal of Physics42(4)pp. 354-361

    Explaining observed properties in terms of underlying shape degrees of freedom is a well–established prism with which to understand atomic nuclei. Self–consistent mean–field models provide one tool to understand nuclear shapes, and their link to other nuclear properties and observables. We present examples of how the time–dependent extension of the mean–field approach can be used in particular to shed light on nuclear shape properties, particularly looking at the giant resonances built on deformed nuclear ground states, and at dynamics in highly-deformed fission isomers. Example calculations are shown of 28Si in the first case, and 240Pu in the latter case.

    M Dutra, O Lourenco, JS Sa Martins, A Delfino, JR Stone, PD Stevenson (2012)Skyrme interaction and nuclear matter constraints, In: PHYSICAL REVIEW C85(3)035201 American Physical Society

    This paper presents a detailed assessment of the ability of the 240 Skyrme interaction parameter sets in the literature to satisfy a series of criteria derived from macroscopic properties of nuclear matter in the vicinity of nuclear saturation density at zero temperature and their density dependence, derived by the liquid-drop model, in experiments with giant resonances and heavy-ion collisions. The objective is to identify those parametrizations which best satisfy the current understanding of the physics of nuclear matter over a wide range of applications. Out of the 240 models, only 16 are shown to satisfy all these constraints. Additional, more microscopic, constraints on the density dependence of the neutron and proton effective mass β-equilibrium matter, Landau parameters of symmetric and pure neutron nuclear matter, and observational data on high- and low-mass cold neutron stars further reduce this number to 5, a very small group of recommended Skyrme parametrizations to be used in future applications of the Skyrme interaction of nuclear-matter-related observables. Full information on partial fulfillment of individual constraints by all Skyrme models considered is given. The results are discussed in terms of the physical interpretation of the Skyrme interaction and the validity of its use in mean-field models. Future work on application of the Skyrme forces, selected on the basis of variables of nuclear matter, in the Hartree-Fock calculation of properties of finite nuclei, is outlined.

    P. D Stevenson, J. M. A Broomfield (2009)Mass Distributions Beyond TDHF, In: AIP Conference Proceedings1098(2009)pp. 133-138

    The mass distributions for giant dipole resonances in S-32 and Sn-132 decaying through particle emission and for deep-inelastic collisions between O-16 nuclei have been investigated by implementing the Balian-Vénéroni variational technique based upon a three-dimensional time-dependent Hartree-Fock code with realistic Skyrme interactions. The mass distributions obtained have been sown to be significantly larger than standard TDHF results.

    PD Stevenson, S Fracasso, EB Suckling, S Freeman, A Andreyev, A Bruce, A Deacon, D Jenkins, D Joss, D MacGregor, P Regan, J Simpson, G Tungate, R Wadsworth, D Watts (2012)The tensor-kinetic field in nuclear collisions, In: RUTHERFORD CENTENNIAL CONFERENCE ON NUCLEAR PHYSICS, 2011381pp. ?-?
    G. A. Jones, P. H. Regan, P. M. Walker, Zs. Podolyák, P. D. Stevenson, M. P. Carpenter, J. J. Carroll, R. S. Chakrawarthy, P. Chowdhury, A. B. Garnsworthy, R. V. F. Janssens, T. L. Khoo, F. G. Kondev, G. J. Lane, Z. Liu, D. Seweryniak, N. J. Thompson, S. Zhu, S. J. Williams (2007)Identification of a high-spin isomer in 99Mo, In: Physical Review C76(047303)
    PG Reinhard, AS Umar, Paul Stevenson, J Piekarewicz,, VE Oberacker, JA Maruhn (2016)Sensitivity of the fusion cross section to the density dependence of the symmetry energy, In: Physical Review C93(4)044618 American Physical Society

    Background: The study of the nuclear equation of state (EOS) and the behavior of nuclear matter under extreme conditions is crucial to our understanding of many nuclear and astrophysical phenomena. Nuclear reactions serve as one of the means for studying the EOS. Purpose: It is the aim of this paper to discuss the impact of nuclear fusion on the EOS. This is a timely subject given the expected availability of increasingly exotic beams at rare isotope facilities [A. B. Balantekin et al., Mod. Phys. Lett. A 29, 1430010 (2014)]. In practice, we focus on 48Ca+48Ca fusion. Method: We employ three different approaches to calculate fusion cross sections for a set of energy density functionals with systematically varying nuclear matter properties. Fusion calculations are performed using frozen densities, using a dynamic microscopic method based on density-constrained time-dependent Hartree-Fock (DC-TDHF) approach, as well as direct TDHF study of above barrier cross sections. For these studies, we employ a family of Skyrme parametrizations with systematically varied nuclear matter properties. Results: The folding-potential model provides a reasonable first estimate of cross sections. DC-TDHF, which includes dynamical polarization, reduces the fusion barriers and delivers much better cross sections. Full TDHF near the barrier agrees nicely with DC-TDHF. Most of the Skyrme forces which we used deliver, on the average, fusion cross sections in good agreement with the data. Trying to read off a trend in the results, we find a slight preferenceforforceswhichdeliveraslopeofsymmetryenergyofL ≈ 50MeVthatcorrespondstoaneutron-skin thickness of 48Ca of Rskin = (0.180–0.210) fm. Conclusions: Fusion reactions in the barrier and sub-barrier region can be a tool to study the EOS and the neutron skin of nuclei. The success of the approach will depend on reduced experimental uncertainties of fusion data as well as the development of fusion theories that closely couple to the microscopic structure and dynamics.

    PD Stevenson, JMA Broomfield (2009)Mass distributions in a variational model, In: REVISTA MEXICANA DE FISICA55(2)pp. 114-118
    RD Page, L Bianco, IG Darby, J Uusitalo, DT Joss, T Grahn, R-D Herzberg, J Pakarinen, J Thomson, S Eeckhaudt, PT Greenlees, PM Jones, R Julin, S Juutinen, S Ketelhut, M Leino, A-P Leppanen, M Nyman, P Rahkila, J Saren, C Scholey, A Steer, MBG Hornillos, JS Al-Khalili, AJ Cannon, PD Stevenson, S Erturk, B Gall, B Hadinia, M Venhart, J Simpson (2007)alpha decay of Re-159 and proton emission from Ta-155, In: PHYSICAL REVIEW C75(6)ARTN 0pp. ?-? AMERICAN PHYSICAL SOC
    R Reifarthl, S Altstadt, K Goebell, T Heftrich, M Heil, A Koloczek, C Langer, R Plag, M Pohl, K Sonnabend, M Weigand, T Adachi, F Aksouh, J Al-Khalili, M AlGarawi, S AlGhamdi, G Alkhazov, N Alkhomashi, H Alvarez-Pol, R Alvarez-Rodriguez, V Andreev, B Andrei, L Atar, T Aumann, V Adeichikov, C Bacri, S Bagchi, C Barbieri, S Beceiro, C Beck, C Beinrucker, G Belier, D Bemmerer, M Bendel, J Benlliure, G Benzoni, R Berjillos, D Bertini, C Bertulani, S Bishop, N Blasi, T Bloch, Y Blumenfeld, A Bonaccorso, K Boretzky, A Botvina, A Boudard, P Boutachkov, I Boztosun, A Bracco, S Brambilla, J Briz Monago, M Caamano, C Caesar, F Camera, E Casarejos, W Catford, J Cederkall, B Cederwall, M Chartier, A Chatillon, M Cherciu, L Chulkov, P Coleman-Smith, D Cortina-Gil, F Crespi, R Crespo, J Cresswell, M Csatlos, F Dechery, B Davids, T Davinson, V Derya, P Detistov, P Diaz Fernandez, D DiJuliot, S Dmitry, D Dore, J Duenas, E Dupont, P Egelhof, I Egorova, Z Elekes, J Enders, J Endres, S Ershov, O Ershova, B Fernandez-Dominguez, A Fetisov, E Fiori, A Fomichev, M Fonseca, L Fraile, M Freer, J Friese, MG Borge, D Galaviz Redondo, S Gannon, U Garg, I Gasparic, L Gasques, B Gastineau, H Geissel, R Gernhaeuser, T Ghosh, M Gilbert, J Glorius, P Golubev, A Gorshkov, A Gourishett, L Grigorenko, J Gulyas, M Haiduc, F Hammache, M Harakeh, M Hass, M Heine, A Hennig, A Henriques, R Herzberg, M Holl, A Ignatov, A Ignatyuk, S Ilieva, M Ivanov, N Iwasa, B Jakobsson, H Johansson, B Jonson, P Joshi, A Junghans, B Jurado, G Koerner, N Kalantar, R Kanungo, A Kelic-Heil, K Kezzar, E Khan, A Khanzadeev, O Kiselev, M Kogimtzis, D Koerper, S Kraeckmann, T Kroell, R Kruecken, A Krasznahorkay, J Kratz, D Kresan, T Krings, A Krumbholz, S Krupko, R Kulessa, S Kumar, N Kurz, E Kuzmin, M Labiche, K Langanke, I Lazarus, T Le Bleis, C Lederer, A Lemasson, R Lemmon, V Liberati, Y Litvinov, B Loeher, J Lopez Herraiz, G Muenzenberg, J Machado, E Maev, K Mahata, D Mancusi, J Marganiec, M Martinez Perez, V Marusov, D Mengoni, B Million, V Morcelle, O Moreno, A Movsesyan, E Nacher, M Najafi, T Nakamura, F Naqvi, E Nikolski, T Nilsson, C Nociforo, P Nolan, B Novatsky, G Nyman, A Ornelas, R Palit, S Pandit, V Panin, C Paradela, V Parkar, S Paschalis, P Pawlowski, A Perea, J Pereira, C Petrache, M Petri, S Pickstone, N Pietralla, S Pietri, Y Pivovarov, P Potlog, A Prokofiev, G Rastrepina, T Rauscher, G Ribeiro, M Ricciardi, A Richter, C Rigollet, K Riisager, A Rios, C Ritter, TR Frutos, J Rodriguez Vignote, M Roeder, C Romig, D Rossi, P Roussel-Chomaz, P Rout, S Roy, P Soederstroem, MS Sarkar, S Sakuta, M Salsac, J Sampson, JS del Rio Saez, J Sanchez Rosado, S Sanjari, P Sarriguren, A Sauerwein, D Savran, C Scheidenberger, H Scheit, S Schmidt, C Schmitt, L Schnorrenberger, P Schrock, R Schwengner, D Seddon, B Sherrill, A Shrivastava, S Sidorchuk, J Silva, H Simon, E Simpson, P Singh, D Slobodan, D Sohler, M Spieker, D Stach, E Stan, M Stanoiu, S Stepantsov, P Stevenson, F Strieder, L Stuhl, T Suda, K Suemmerer, B Streicher, J Taieb, M Takechi, I Tanihata, J Taylor, O Tengblad, G Ter-Akopian, S Terashima, P Teubig, R Thies, M Thoennessen, T Thomas, J Thornhill, G Thungstrom, J Timar, Y Togano, U Tomohiro, T Tornyi, J Tostevin, C Townsley, W Trautmann, T Trivedi, S Typel, E Uberseder, J Udias, T Uesaka, L Uvarov, Z Vajta, P Velho, V Vikhrov, M Volknandt, V Volkov, P von Neumann-Cose, M von Schmid, A Wagner, F Wamers, H Weick, D Wells, L Westerberg, O Wieland, M Wiescher, C Wimmer, K Wimmer, JS Winfield, M Winkel, P Woods, R Wyss, D Yakorev, M Yavor, JZ Cardona, I Zartova, T Zerguerras, I Zgura, A Zhdanov, M Zhukov, M Zieblinski, A Zilges, K Zuber (2016)Nuclear astrophysics with radioactive ions at FAIR, In: Nuclear Physics in Astrophysics VI (NPA6). Journal of Physics: Conference Series665(1)

    The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process, β-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.

    PM Goddard, N Cooper, V Werner, G Rusev, PD Stevenson, A Rios, C Bernards, A Chakraborty, BP Crider, J Glorius, RS Ilieva, JH Kelley, E Kwan, EE Peters, N Pietralla, R Raut, C Romig, D Savran, L Schnorrenberger, MK Smith, K Sonnabend, AP Tonchev, W Tornow, SW Yates (2013)Dipole response of $^76$Se above 4 MeV, In: Phys. Rev. C88(6)pp. 064308-064308 American Physical Society

    The dipole response of 76 34 Se in the energy range from 4 to 9 MeV has been analyzed using a (γ ⃗ ,γ ′ ) polarized photon scattering technique, performed at the High Intensity γ -Ray Source facility at Triangle Universities Nuclear Laboratory, to complement previous work performed using unpolarized photons. The results of this work offer both an enhanced sensitivity scan of the dipole response and an unambiguous determination of the parities of the observed J=1 states. The dipole response is found to be dominated by E1 excitations, and can reasonably be attributed to a pygmy dipole resonance. Evidence is presented to suggest that a significant amount of directly unobserved excitation strength is present in the region, due to unobserved branching transitions in the decays of resonantly excited states. The dipole response of the region is underestimated when considering only ground state decay branches. We investigate the electric dipole response theoretically, performing calculations in a three-dimensional (3D) Cartesian-basis time-dependent Skyrme-Hartree-Fock framework.

    M Avgoulea, YP Gangrsky, KP Marinova, SG Zemlyanoi, S Fritzsche, D Iablonskyi, C Barbieri, EC Simpson, PD Stevenson, J Billowes, P Campbell, B Cheal, B Tordoff, ML Bissell, DH Forest, MD Gardner, G Tungate, J Huikari, A Nieminen, H Penttila, J Aysto (2011)Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS38(2)ARTN 0pp. ?-? IOP PUBLISHING LTD
    M Kaur, BR Behera, G Singh, V Singh, N Madhavan, S Muralithar, S Nath, J Gehlot, G Mohanto, I Mukul, D Siwal, M Thakur, K Kapoor, P Sharma, T Banerjee, A Jhingan, T Varughese, I Bala, BK Nayak, A Saxena, MB Chatterjee, PD Stevenson (2016)Probing dynamics of fusion reactions through cross-section and spin distribution measurement, In: EPJ Web of Conferences117

    Present work aims to explicate the effect of entrance channel mass asymmetry on fusion dynamics for the Compound Nucleus 80Sr populated through two different channels, 16O+64Zn and 32S+48Ti, using cross-section and spin distribution measurements as probes. The evaporation spectra studies for these systems, reported earlier indicate the presence of dynamical effects for mass symmetric 32S+48Ti system. The CCDEF and TDHF calculations have been performed for both the systems and an attempt has been made to explain the reported deviations in the α-particle spectrum for the mass symmetric system.

    DT Joss, IG Darby, RD Page, J Uusitalo, S Eeckhaudt, T Grahn, PT Greenlees, PM Jones, R Julin, S Juutinen, S Ketelhut, M Leino, AP Leppänen, M Nyman, J Pakarinen, P Rahkila, J Sarén, C Scholey, AN Steer, JS Al-Khalili, AJ Cannon, PD Stevenson, S Ertürk, B Gall, B Hadinia, M Venhart, J Simpson (2007)Discovery of the proton emitting nucleus 159Re, In: AIP Conference Proceedings961pp. 28-33

    The observation of the new nuclide 159Re provides important insights into the evolution of single-particle structure in heavy nuclei beyond the proton drip line. The nuclide 159Re was synthesised in the reaction 106Cd(58Ni, p4n) and identified via its proton radioactivity using the RITU gas-filled separator and the GREAT focal-plane spectrometer. Comparisons of the measured proton energy (Ep = 1805±20 keV) and decay half-life (t1/2 = 21±4 μs) with values calculated using the WKB method indicate that the proton is emitted from an h11/2 state. The implications of these results for future experimental investigations into even more proton unbound Re isotopes using in-flight separation techniques are considered. © 2007 American Institute of Physics.

    JR Stone, PD Stevenson, MR Strayer (2002)At the N=Z line and beyond: HF+BCS mean-field calculations with the separable monopole interaction., In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY224pp. U92-U92 AMER CHEMICAL SOC
    E.A Cryer-Jenkins, Paul Stevenson (2020)Gamow’s Cyclist: A New Look at Relativistic Measurements for a Binocular Observer, In: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences The Royal Society

    The visualisation of objects moving at relativistic speeds has been a popular topic of study since Special Relativity’s inception. While the standard exposition of the theory describes certain shapechanging effects, such as the Lorentz-contraction, it makes no mention of how an extended object would appear in a snapshot or how apparent distortions could be used for measurement. Previous work on the subject has derived the apparent form of an object, often making mention of George Gamow’s relativistic cyclist thought experiment. Here, a rigorous reanalysis of the cyclist, this time in 3-dimensions, is undertaken for a binocular observer, accounting for both the distortion in apparent position and the relativistic colour and intensity shifts undergone by a fast moving object. A methodology for analysing binocular relativistic data is then introduced, allowing the fitting of experimental readings of an object’s apparent position to determine the distance to the object and its velocity. This method is then applied to the simulation of Gamow’s cyclist, producing selfconsistent results.

    PAUL DENIS STEVENSON Comments on Quantum Computing in Nuclear Physics, In: International journal of unconventional computing

    We review recent research on quantum computing applications for calculations and simulation of nuclear physics. As systems of interacting fermions, nuclei and their quantum simulation bears much similarity to the quantum computation of chemical systems , whose studies are relatively more advanced. Hence techniques from the quantum chemistry literature may be readily adopted. Some ways in which nuclei differ from other many-body systems, such as the strong non-perturbative interaction, are highlighted, and a selection of existing results are discussed, covering nuclear structure and reactions.

    PH Regan, N Alkhomashi, N Al-Dahan, Z Podolyak, EB Suckling, PD Stevenson, SB Pietri, SJ Steer, AB Garnsworthy, W Gelletly, J Benlliure, AI Morales, J Gerl, M Gorska, HJ Wollersheim, R Kumar, J Grebosz, A Algora, G Benzoni, P Boutachkov, AM Bruce, E Casarejos, IJ Cullen, AMD Bacelar, A Blazhev, ME Estevez, G Farrelly, Y Fujita, R Hoischen, S Lalkovski, Z Liu, I Kojouharov, N Kurz, C Mihai, F Molina, D Muecher, B Rubio, H Schaffner, S Tashenov, A Tamii, JJV Dobon, PM Walker, PJ Woods, A Blazhev, J Jolie, N Warr, A Zilges (2009)New Insights into the Structure of Exotic Nuclei Using the RISING Active Stopper, In: CAPTURE GAMMA-RAY SPECTROSCOPY AND RELATED TOPICS1090pp. 122-129
    Yu Qiang, Junchen Pei, Paul Stevenson (2021)Fission Dynamics of Compound Nuclei: Pairing versus Fluctuations, In: Physical review. C103(3)L031304 American Physical Society

    Phys. Rev. C 103, 031304 (2021) Energy dependence of fission observables is a key issue for wide nuclear applications. We studied real-time fission dynamics from low-energy to high excitations in the compound nucleus $^{240}$Pu with the time-dependent Hartree-Fock+BCS approach. It is shown that the evolution time of the later phase of fission towards scission is considerably lengthened at finite temperature. As the role of dynamical pairing is vanishing at high excitations, the random transition between single-particle levels around the Fermi surface to mimic thermal fluctuations is indispensable to drive fission. The obtained fission yields and total kinetic energies with fluctuations can be divided into two asymmetric scission channels, namely S1 and S2, which explain well experimental results, and give microscopic support to the Brosa model. With increasing fluctuations, S2 channel takes over S1 channel and the spreading fission observables are obtained.

    L Bianco, RD Page, IG Darby, DT Joss, J Simpson, JS Al-Khalili, AJ Cannon, B Cederwall, S Eeckhaudt, S Ertürk, B Gall, MBG Hornillos, T Grahn, PT Greenlees, B Hadinia, K Heyde, U Jakobsson, PM Jones, R Julin, S Juutinen, S Ketelhut, M Labiche, M Leino, A-P Leppänen, M Nyman, D O'Donnell, ES Paul, M Petri, P Peura, A Puurunen, P Rahkila, P Ruotsalainen, M Sandzelius, PJ Sapple, J Sarén, C Scholey, NA Smirnova, AN Steer, PD Stevenson, EB Suckling, J Thomson, J Uusitalo, M Venhart (2010)Discovery of 157W and 161Os, In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics690(1)pp. 15-18
    PD Stevenson (2003)Automatic generation of vacuum amplitude many-body perturbation series, In: INTERNATIONAL JOURNAL OF MODERN PHYSICS C14(8)pp. 1135-1141 WORLD SCIENTIFIC PUBL CO PTE LTD
    PM Goddard, PD Stevenson, A Rios (2013)Charge radius isotope shift across the N=126 shell gap, In: Physical Review Letters110(3) American Physical Society

    We revisit the problem of the kink in the charge radius shift of neutron-rich even isotopes near the N=126 shell closure. We show that the ability of a Skyrme force to reproduce the isotope shift is determined by the occupation of the neutron 1i orbital beyond N=126 and the corresponding change it causes to deeply-bound protons orbitals with a principal quantum number of 1. Given the observed position of the single-particle energies, one must either ensure occupation is allowed through correlations, or not demand that the single-particle energies agree with experimental values at the mean-field level. © 2013 American Physical Society.

    PD Stevenson (2015)Numerical Calculations of TDHF, In: Y Iwata (eds.), Progress of time-dependent nuclear reaction theory Bentham Science Publishers

    We discuss some aspects of implementing the time-dependent Hartree-Fock method in the case of nuclear physics. Topics discussed include implementation of the time-stepping algorithm, considerations involving the ef- fective interaction, and the use (or not) of particular optional terms in the energy density functional, and boundary conditions. Examples of application of the technique to giant resonances and reactions are given, concentrating on issues to do with numerical and conceptual interpretation.

    Yoritaka Iwata, Paul Stevenson (2019)Conditional recovery of time-reversal symmetry in many nucleus systems, In: New Journal of Physics IOP Publishing

    The propagation of non-topological solitons in many-nucleus systems is studied based on timedependent density functional calculations, focusing on mass and energy dependence. The dispersive property and the nonlinearity of the system, which are inherently included in the nuclear density functional, are essential factors to form a non-topological soliton. On the other hand, soliton propagation is prevented by charge equilibration, and competition can appear between soliton formation and disruption. In this article, based on the energy-dependence of the two competitive factors, the concept of conditional recovery of time-reversal symmetry is proposed in many-nucleus systems. It clarifies the possibility of preserving the nuclear medium inside natural or artificial nuclear reactors, at a suitable temperature. From an astrophysical point of view, the existence of the low-temperature solitonic core of compact stars is suggested.

    PD Stevenson, S Fracasso, EB Suckling (2012)The tensor-kinetic field in nuclear collisions, In: Journal of Physics: Conference Series3811pp. 012105-012105 Institute of Physics

    The role of the tensor terms in the Skyrme interaction is studied for their effect in dynamic calculations where non-zero contributions to the mean-field may arise, even when the starting nucleus, or nuclei are even-even and have no active time-odd potentials in the ground state. We study collisions in the test-bed 16 O- 16 O system, and give a qualitative analysis of the behaviour of the time-odd tensor-kinetic density, which only appears in the mean field Hamiltonian in the presence of the tensor force. We find an axial excitation of this density is induced by a collision.

    Paul Stevenson, EB Suckling, S Fracasso, Matthew Barton, AS Umar (2016)The Skyrme Tensor Force in Heavy Ion Collisions, In: Physical Review C93054617 American Physical Society

    Background: It is generally acknowledged that the time-dependent Hartree-Fock (TDHF) method provides a useful foundation for a fully microscopic many-body theory of low-energy heavy-ion reactions. The TDHF method is also known in nuclear physics in the small amplitude domain, where it provides a useful description of collective states, and is based on the mean-field formalism which has been a relatively successful approximation to the nuclear many-body problem. Currently, the TDHF theory is being widely used in the study of fusion excitation functions, fission, deep-inelastic scattering of heavy mass systems, while providing a natural foundation for many other studies. Purpose: With the advancement of computational power it is now possible to undertake TDHF calculations without any symmetry assumptions and incorporate the major strides made by the nuclear structure community in improving the energy density functionals used in these calculations. In particular, time-odd and tensor terms in these functionals are naturally present during the dynamical evolution, while being absent or minimally important for most static calculations. The parameters of these terms are determined by the requirement of Galilean invariance or local gauge invariance but their significance for the reaction dynamics have not been fully studied. This work addresses this question with emphasis on the tensor force. Method: The full version of the Skyrme force, including terms arising only from the Skyrme tensor force, is applied to the study of collisions within a completely symmetry-unrestricted TDHF implementation. Results: We examine the effect on upper fusion thresholds with and without the tensor force terms and find an effect on the fusion threshold energy of the order several MeV. Details of the distribution of the energy within terms in the energy density functional is also discussed. Conclusions: Terms in the energy density functional linked to the tensor force can play a non-negligible role in dynamic processes in nuclei.

    N Loebl, AS Umar, JA Maruhn, P-G Reinhard, Paul Stevenson, VE Oberacker (2012)Single-particle dissipation in a time-dependent Hartree-Fock approach studied from a phase-space perspective, In: PHYSICAL REVIEW C86(2)ARTN 0pp. ?-? AMER PHYSICAL SOC
    P. H. Regan, F. R. Xu, P. M. Walker, M. Oi, A. K. Rath, P. D. Stevenson (2002)Structure of the doubly midshell nucleus 66170Dy104, In: Physical Review C65(037302)
    PM Walker, S Lalkovski, PD Stevenson (2010)Configuration dependence of K-forbidden transition rates from three-quasiparticle isomers, In: PHYSICAL REVIEW C81(4)ARTN 0pp. ?-? AMER PHYSICAL SOC
    D Almehed, PD Stevenson (2005)Isoscalar and isovector giant monopole resonances using TDHF, In: Z Gacsi, Z Dombradi, A Krasznahorkay (eds.), EXOTIC NUCLEAR SYSTEMS802pp. 305-308
    BK Sharma, SK Patra, RK Gupta, A Shukla, P Arumugam, PD Stevenson, W Greiner (2006)Reaction cross-sections for light nuclei on C-12 using relativistic mean field formalism, In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS32(11)pp. 2089-2097 IOP PUBLISHING LTD
    J A Maruhn, P G Reinhard, P D Stevenson, J R Stone, M R Strayer (2005)Dipole Giant Resonances in Deformed Heavy Nuclei, In: Physical Review C71(6)

    The spectral distribution of isovector dipole strength is computed using the time-dependent Skyrme-Hartree-Fock method with subsequent spectral analysis. The calculations are done without any imposed symmetry restriction, allowing any nuclear shape to be dealt with. The scheme is used to study the deformation dependence of giant resonances and its interplay with Landau fragmentation (owing to 1 ph states). Results are shown for the chain of Nd isotopes, superdeformed Dy-152, triaxial Os-188, and U-238.

    PM Goddard, PD Stevenson, A Rios (2013)Charge Radius Isotope Shift Across the N=126 Shell Gap, In: Physical Review Letters110

    We revisit the problem of the kink in the charge radius shift of neutron-rich even isotopes near the N=126 shell closure. We show that the ability of a Skyrme force to reproduce the isotope shift is determined by the occupation of the neutron 1i11/2 orbital beyond N=126 and the corresponding change it causes to deeply-bound protons orbitals with a principal quantum number of 1. Given the observed position of the single-particle energies, one must either ensure occupation is allowed through correlations, or not demand that the single-particle energies agree with experimental values at the mean-field level.

    P. D. Stevenson (2020)Role of the Surface Energy in Heavy-Ion Collisions, In: EPJ Web of Conferences232pp. 03005-1 EDP Sciences

    The surface energy is one of the fundamental properties of nuclei, appearing in the simplest form of the semi-empirical mass formula. The surface energy has an influence on e.g. the shape of a nucleus and its ability to deform. This in turn could be expected to have an effect in fusion reactions around the Coulomb barrier where dynamical effects such as the formation of a neck is part of the fusion process. Frozen Hartree-Fock and Time-Dependent Hartree-Fock calculations are performed for a series of effective interactions in which the surface energy is systematically varied, using 40Ca + 48Ca as a test case. The dynamical lowering of the barrier is greatest for the largest surface energy, contrary to naive expectations, and we speculate that this may be due to the variation in other nuclear matter properties for these effective interactions.

    Paul Stevenson (2020)Internuclear potentials from the Sky3D code, In: IOP Scinotes IOP Publishing

    This note presents a minor alteration to, and subsequent use of, the Sky3D nuclear time-dependent Hartree-Fock code to calculate ion-ion potentials in the Frozen Hartree-Fock approximation. An example of 16O + 16O is presented.