Natalia Timofeyuk

Dr Natalia Timofeyuk


Senior Research Fellow
PhD
+44 (0)1483 689375
02 BB 03

Academic and research departments

Department of Physics.

Research

Research interests

Research projects

Research collaborations

My publications

Publications

Mukha I, Timofeyuk NK, Sümmerer K, Acosta L, Alvarez MAG, Casarejos E, Chatillon A, Cortina-Gil D, Espino JM, Fomichev A, García-Ramos JE, Geissel H, Gómez-Camacho J, Grigorenko L, Hofmann J, Kiselev O, Korsheninnikov A, Kurz N, Litvinov Y, Martel I, Nociforo C, Ott W, Pfützner M, Rodríguez-Tajes C, Roeckl E, Stanoiu M, Weick H, Woods PJ (2009) Observation of narrow states in nuclei beyond the proton drip line: F15 and Ne16, Physical Review C - Nuclear Physics 79 (6)
Two high-lying states in F15 and Ne16, unbound with respect to one-proton (1p) and two-proton (2p) emissions, have been observed in the fragmentation of Ne17 at intermediate energies. They undergo mainly sequential emissions of protons via intermediate states in O14 and F15 and have decay energies of 7.8(2) and 7.6(2) MeV, respectively. The widths of the newly observed states in F15 and Ne16 are much smaller than the Wigner limits for single-particle configurations, of 0.4(4) and 0.8(+8-4) MeV, respectively. In addition, narrow widths of 0.2(2) MeV are derived for two other high-lying states in F15 with Qp of 4.9 and 6.4 MeV, which match features of the recently predicted narrow odd-parity F15 states with two valence protons in the sd shell. All energies and widths have been obtained by analyzing angular correlations of the decay products, p-p-O14 and p-p-N13, whose trajectories have been measured by a tracking technique with silicon microstrip detectors. © 2009 The American Physical Society.
Timofeyuk NK, Descouvemont P (2010) Narrow states in the three-proton emitter Na-17,PHYSICAL REVIEW C 81 (5) ARTN 051301
Timofeyuk NK (2011) Properties of one-nucleon overlap functions for Ae16 double-closed-shell nuclei in the source-term approach,Physical Review C - Nuclear Physics 84 (5) 054313 American Physical Society
Descouvemont P, Dufour M, Timofeyuk N (2013) Core excitations in exotic nuclei,Journal of Physics: Conference Series 436 (1)
The role of core excitations in exotic nuclei is discussed in the framework of a microscopic cluster model. This cluster approach is complemented by the R-matrix theory to take account of the long-range part of the wave functions. We briefly describe the model, and present two recent examples: the neutron-rich nucleus 16B, described by a 15B+n structure, and the proton-rich nucleus 17Na, described by a 16Ne+p structure. In both cases core excitations are shown to play an important role.
Timofeyuk N, Johnson RC (2013) Nonlocality in Deuteron Stripping Reactions,PHYSICAL REVIEW LETTERS 110 (11) ARTN 1 AMER PHYSICAL SOC
We propose a new method for the analysis of deuteron stripping reactions, A(d,p)B, in which the nonlocality of nucleon-nucleus interactions and three-body degrees of freedom are accounted for in a consistent way. The model deals with equivalent local nucleon potentials taken at an energy shifted by
Timofeyuk Natalia, Baye D. (2017) Hyperspherical Harmonics Expansion on Lagrange Meshes for Bosonic Systems in One Dimension,Few-Body Systems 58 (6) Springer Vienna
A one-dimensional system of bosons interacting with contact and single-Gaussian forces is studied with an expansion in hyperspherical harmonics. The hyperradial potentials are calculated using the link between the hyperspherical harmonics and the single-particle harmonic-oscillator basis while the coupled hyperradial equations are solved with the Lagrange-mesh method. Extensions of this method are proposed to achieve good convergence with small numbers of mesh points for any truncation of hypermomentum. The convergence with hypermomentum strongly depends on the range of the two-body forces: it is very good for large ranges but deteriorates as the range decreases, being the worst for the contact interaction. In all cases, the lowest-order energy is within 4.5% of the exact solution and shows the correct cubic asymptotic behaviour at large boson numbers. Details of the convergence studies are presented for 3, 5, 20 and 100 bosons. A special treatment for three bosons was found to be necessary. For single-Gaussian interactions, the convergence rate improves with increasing boson number, similar to what happens in the case of three-dimensional systems of bosons.
Kievsky A, Timofeyuk NK, Gattobigio M (2014) $N$-boson spectrum from a Discrete Scale Invariance,PHYSICAL REVIEW A
We present the analysis of the $N$-boson spectrum computed using a soft
two-body potential the strength of which has been varied in order to cover an
extended range of positive and negative values of the two-body scattering
length $a$ close to the unitary limit. The spectrum shows a tree structure of
two states, one shallow and one deep, attached to the ground-state of the
system with one less particle. It is governed by an unique universal function,
$\Delta(\xi)$, already known in the case of three bosons. In the three-particle
system the angle $\xi$, determined by the ratio of the two- and three-body
binding energies $E_3/E_2=\tan^2\xi$, characterizes the Discrete Scale
Invariance of the system. Extending the definition of the angle to the $N$-body
system as $E_N/E_2=\tan^2\xi$, we study the $N$-boson spectrum in terms of this
variable. The analysis of the results, obtained for up to $N=16$ bosons, allows
us to extract a general formula for the energy levels of the system close to
the unitary limit. Interestingly, a linear dependence of the universal function
as a function of $N$ is observed at fixed values of $a$. We show that the
finite-range nature of the calculations results in the range corrections that
generate a shift of the linear relation between the scattering length $a$ and a
particular form of the universal function. We also comment on the limits of
applicability of the universal relations.
Fernández-Domínguez B, Pereira-López X, Timofeyuk NK, Descouvemont P, Catford WN, Delaunay F (2015) Spectroscopic study of the exotic nucleus P 25,Physical Review C - Nuclear Physics 91 (2)
© 2015 American Physical Society.Motivated by the importance of P25 for the two-proton decay of S26 and for searches of the mirror analog of the island of inversion near N=16, we present the first predictions for the spectroscopy of the exotic isotope P25 obtained in the shell model, a potential model, and a microscopic-cluster model. All models predict P25 to be unbound, with an energy in the range 0.78-1.03 MeV, which favors previous mass systematics over more recent revisions. We show that P25 possesses a rich low-lying spectrum that should be accessible by experimental studies. All of the predicted states below 7 MeV, except one, are narrow. Many of them are built on the excited-core states of 24Si for which the Coulomb barrier is raised. For decays into the 24Si(g.s.)+p channel we determined the proton widths based on their link to the asymptotic normalization coefficients (ANCs) of their mirror analogs in 25Ne. We determine these ANCs from the analysis of the transfer reaction 24Ne(d,p)25Ne. The proton widths for decay into excited-state channels are obtained in model calculations. The only broad state is the intruder 3/2-, the mirror analog of which has been recently observed in 25Ne. The 25P(3/2-) energy is lower than that in 25Ne, suggesting that the island of inversion may persist on the proton-rich side. All excited states of P25 have at least two decay modes and are expected to populate variously the 21,2+ and 4+ states in 24Si, which then decay electromagnetically.
Timofeyuk NK, Baye D, Descouvemont P, Kamouni R, Thompson IJ (2006) C15-F15 charge symmetry and the C14(n,³)C15 reaction Puzzle,Physical Review Letters 96 (16)
The low-energy reaction C14(n,³)C15 provides a rare opportunity to test indirect methods for the determination of neutron capture cross sections by radioactive isotopes versus direct measurements. It is also important for various astrophysical scenarios. Currently, puzzling disagreements exist between the C14(n,³)C15 cross sections measured directly, determined indirectly, and calculated theoretically. To solve this puzzle, we offer a strong test based on a novel idea that the amplitudes for the virtual C15’C14+n and the real F15’O14+p decays are related. Our study of this relation, performed in a microscopic model, shows that existing direct and some indirect measurements strongly contradict charge symmetry in the C15 and F15 mirror pair. This brings into question the experimental determinations of the astrophysically important (n,³) cross sections for short-lived radioactive targets. © 2006 The American Physical Society.
Fomichev AS, Ter-Akopian GM, Bezbakh AA, Chudoba V, Daniel AV, Golovkov MS, Gorshkov AV, Gorshkov VA, Grigorenko LV, Kaminski G, Krupko SA, Oganessian YT, Parfenova YL, Sidorchuk SI, Slepnev RS, Standylo L, Stepantsov SV, Wolski R, Ershov SN, Lukyanov VK, Danilin BV, Korsheninnikov AA, Goldberg VZ, Pfützner M, Mukha IG, Simon H, Tarasov OB, Timofeyuk NK, Zhukov MV (2012) Status of the ACCULINNA-2 project at FLNR,Journal of Physics: Conference Series 337 (1)
The project of a new and more powerful in-flight fragment separator ACCULINNA-2 at U-400M cyclotron in FLNR, JINR planned to build in addition to the existing separator ACCULINNA is presented. The new separator will provide high intensity RIBs in the lowest energy range (5÷50 MeV/nucleon) which is attainable for in-flight separators. The possibilities for the astrophysics studies at the proposed device are presented. ACCULINNA-2 separator is planned to be constructed in the years 2010-2015. The current status of the project is reported.
Timofeyuk NK, Fernandez-Dominguez B, Descouvemont P, Catford WN, Delaunay F, Thomas JS (2012) Core excitations and narrow states beyond the proton dripline: The exotic nucleus Al-21,PHYSICAL REVIEW C 86 (3) ARTN 034305 AMER PHYSICAL SOC
Timofeyuk NK (2012) Convergence of the hyperspherical-harmonics expansion with increasing number of particles for bosonic systems,Physical Review A - Atomic, Molecular, and Optical Physics 86 (3)
A formal proof is given that for N-boson systems in which two-body interaction potentials are described by a single Gaussian the ratio of higher-order to the lowest-order hyper-radial potentials decreases at N’? as N -1 /2 or faster. As a result, for such potentials, the convergence of binding energies for ground and several lowest excited states, obtained in expansion of the N-body wave function over the hyperspherical-harmonics basis, improves with increasing number of bosons. For a phenomenological three-body repulsive potential, introduced to account for the missing hard core, the ratio of higher-order to lowest-order hyper-radial potential, corresponding to this three-body potential, also decreases as N -1 /2 or faster when N’?. Although adding the three-body contributions leads to increased influence from the total nondiagonal couplings around the node of the lowest hyper-radial potential, the arguments are given that this should not dramatically deteriorate the convergence if the range of repulsion is properly chosen. This means that the hyperspherical- harmonics expansion with soft two-body and repulsive three-body effective forces may become an attractive tool for studying the spectra of many-body systems. It is suggested that fine tuning of the three-body repulsion to reproduce the binding energies over a large region of N is possible. In particular, it has been shown that an N-independent choice for the three-body repulsion exists for which the ground-state binding energies of Nd112 atoms of helium, obtained in the lowest-order approximation of the hyperspherical-harmonics expansion, are close to the prediction of the Green's function Monte Carlo method with a hard-core He-He potential. © 2012 American Physical Society.
Timofeyuk NK, Descouvemont P, Johnson RC (2007) Isospin symmetry in mirror ± decays, Physical Review C - Nuclear Physics 75 (3)
We show that a consequence of isospin symmetry, recently discovered in mirror conjugated one-nucleon decays, can be extended to mirror-conjugated ±-particle decays, both virtual and real. For virtual ± decays of bound mirror pairs this symmetry manifests itself as a relation between the asymptotic normalization coefficients (ANCs) of ±-particle overlap integrals. This relation is given by a simple analytical formula that involves ±-particle separation energies and charges of residual nuclei. For bound-unbound mirror pairs, the ANC of a bound nucleus is related to the ± width of the mirror unbound level. For unbound mirror pairs we get a new analytical formula that relates the widths of mirror resonances. We test the validity of these analytical formulas against the predictions of a two-body potential and of a many-body microscopic cluster model for several mirror states in Li7-Be7, B11-C11, and F19-Ne19 isotopes. We show that these analytical formulas are valid in many cases but that some deviations can be expected for isotopes with strongly deformed and easily excited cores. In general, the results from microscopic model are not very sensitive to model assumptions and can be used to predict unknown astrophysically relevant cross sections using known information about mirror systems. © 2007 The American Physical Society.
Timofeyuk NK, Johnson RC (2013) Publisher's Note: Nonlocality in deuteron stripping reactions, Physical Review Letters 110 (13)
Timofeyuk NK, Thompson IJ (2008) Spectroscopic factors and asymptotic normalization coeffcients in mirror three-body systems, PHYSICAL REVIEW C 78 (5) ARTN 054322
Timofeyuk NK, Johnson RC, Mukhamedzhanov AM (2006) Relation between proton and neutron asymptotic normalization coefficients for light mirror nuclei and its relevance to nuclear astrophysics (vol 91, pg 232501, 2003), PHYSICAL REVIEW LETTERS 97 (6) ARTN 069904
Timofeyuk NK (2014) Overlap functions for reaction theories: Challenges and open problems, Journal of Physics G: Nuclear and Particle Physics 41 (9)
© 2014 IOP Publishing Ltd. The overlap functions between the nuclear wave functions in initial and final states are important structural quantities that enter the amplitudes of nuclear reactions such as transfer, knockout and radiative capture. They carry information about the single-particle structure and about the nucleon-nucleon interactions and correlations in atomic nuclei. The current status of knowledge of overlap functions is reviewed with an emphasis on their theoretical calculation. The open problems associated with their prediction are highlighted and challenges are discussed.
Yakhelef A, Timofeyuk NK, Al-Khalili JS, Thompson IJ (2010) Three-Body Spectrum of C-18 and its Relevance to r-Process Nucleosynthesis, FEW-BODY SYSTEMS 47 (4) pp. 213-224 SPRINGER WIEN
Fomichev AS, Chudoba V, Daniel AV, Golovkov MS, Gorshkov AV, Gorshkov VA, Grigorenko LV, Kaminski G, Krupko SA, Oganessian YT, Sidorchuk SI, Slepnev RS, Stepantsov SV, Tarasov OB, Ter-Akopian GM, Wolski R, Ershov SN, Lukyanov VK, Danilin BV, Korsheninnikov AA, Goldberg VZ, Mukha IG, Simon H, Pfutzner M, Timofeyuk NK, Zhukov MV (2011) Long range plan with radioactive beams at Dubna, 3rd International Conference on Current Problems in Nuclear Physics and Atomic Energy, NPAE 2010 - Proceedings pp. 64-69
A program for upgrade of existing radioactive ion beams facilities at Flerov Laboratory of Nuclear Reactions, JINR Dubna is presented. A project of a new in-flight fragment separator ACCULINNA-2 is proposed. It is expected the new instrument will be more universal and powerful than the existing nowadays. The beam intensity should be increased by factor 10-15, its optical quality greatly improved and the range of the accessible secondary radioactive beams broadened up to Z
We show how the charge symmetry of strong interactions can be used to relate
the proton and neutron asymptotic normalization coefficients (ANCs) of the one
nucleon overlap integrals for light mirror nuclei. This relation extends to the
case of real proton decay where the mirror analog is a virtual neutron decay of
a loosely bound state. In this case, a link is obtained between the proton
width and the squared ANC of the mirror neutron state. The relation between
mirror overlaps can be used to study astrophysically relevant proton capture
reactions based on information obtained from transfer reactions with stable
beams.
Krupko SA, Fomichev AS, Chudoba V, Daniel AV, Golovkov MS, Gorshkov VA, Grigorenko LV, Oganessian YT, Sidorchuk SI, Slepnev RS, Stepantsov SV, Tarasov OB, Ter-Akopian GM, Wolski R, Ershov SN, Lukyanov VK, Danilin BV, Korsheninnikov AA, Goldberg VZ, Mukha IG, Simon H, Pfutzner M, Timofeyuk NK, Zhukov MV, Lawrie K, Newman RT (2010) Fragment separator ACCULINNA-2,AIP Conference Proceedings 1224 pp. 516-521
Project of a new in?flight fragment separator is proposed as a part of the third generation DRIBs facilities in Dubna. As compared to the existing separator ACCULINNA, beam intensity should be increased by a factor 10?15, the beam quality improved and the RIB assortment should broaden considerably at ACCULINNA?2. Research program and structure are outlined for the new instrument.
Experimental studies of one-nucleon knockout from magic nuclei suggest that their nucleon orbits are not fully occupied. This conflicts a commonly accepted view of the shell closure associated with such nuclei. The conflict can be reconciled if the overlap between initial and final nuclear states in a knockout reaction are calculated by a nonstandard method. The method employs an inhomogeneous equation based on correlation-dependent effective nucleon-nucleon interactions and allows the simplest wave functions, in which all nucleons occupy only the lowest nuclear orbits, to be used. The method also reproduces the recently established relation between reduction of spectroscopic strength, observed in knockout reactions on other nuclei, and nucleon binding energies. The implication of the inhomogeneous equation method for the physical meaning of spectroscopic factors is discussed.
Johnson RC, Timofeyuk NK (2014) Adiabatic model of $(d,p)$ reactions with explicitly energy-dependent
non-local potentials
,
Physical Review C: Nuclear Physics
We have developed an approximate way of dealing with explicit
energy-dependence of non-local nucleon optical potentials as used to predict
the $(d,p)$ cross sections within the adiabatic theory. Within this
approximation, the non-local optical potentials have to be evaluated at an
energy shifted from half the incident deuteron energy by the $n-p$ kinetic
energy averaged over the range of the $n-p$ interaction and then treated as an
energy-independent non-local potential. Thus the evaluation of the distorting
potential in the incident channel is reduced to a problem solved in our
previous work in [{\it Phys. Rev. Lett. 110, 112501(2013) and Phys. Rev. C 87,
064610 (2013)}]. We have demonstrated how our new model works for the case of
$^{16}$O$(d,p)^{17}$O, $^{36}$Ar($d,p)^{37}$Ar and $^{40}$Ca$(d,p)^{41}$Ca
reactions and highlighted the need for a detailed understanding of
energy-dependence of non-local potentials. We have also suggested a simple way
of correcting the $d-A$ effective potentials for non-locality when the
underlying energy-dependent non-local nucleon potentials are unknown but
energy-dependent local phenomenological nucleon potentials are available.
Timofeyuk NK (2008) Improved procedure to construct a hyperspherical basis for the N-body problem: Application to bosonic systems, Physical Review C - Nuclear Physics 78 (5) 054314 pp. 1-8
A new procedure to construct hyperspherical harmonics is presented in which the matrix of the multidimensional hyperangular Laplacian is diagonalized in the single-particle oscillator basis. It is shown that this matrix can be constructed and diagonalized prior to the elimination of spurious states in small subspaces, and that calculations of only the two-body operators is required. As a result, the hyperspherical basis can be constructed much faster than in the procedure introduced earlier [N. K. Timofeyuk, Phys. Rev. C 65, 064306 (2002)], which is based on recursive elimination of hyperradial excitations. The applicability of the proposed method is demonstrated for the systems made of up to ten identical bosons with zero spin using two different two-body potentials. In particular, it has been applied to some ±-particle nuclei for which the projection of their 0+ wave functions into the ?condensed state wave function? have been calculated.
Timofeyuk NK, Baye D, Descouvemont P, Kamouni R, Thompson IJ (2006) 15C-15F Charge symmetry and the 14C(n,gamma)15C reaction puzzle.,Phys Rev Lett 96 (16) The American Physical Society
The low-energy reaction 14C(n,gamma)15C provides a rare opportunity to test indirect methods for the determination of neutron capture cross sections by radioactive isotopes versus direct measurements. It is also important for various astrophysical scenarios. Currently, puzzling disagreements exist between the 14C(n,gamma)15C cross sections measured directly, determined indirectly, and calculated theoretically. To solve this puzzle, we offer a strong test based on a novel idea that the amplitudes for the virtual 15C-->14C + n and the real 15F -->14O + p decays are related. Our study of this relation, performed in a microscopic model, shows that existing direct and some indirect measurements strongly contradict charge symmetry in the 15C and 15F mirror pair. This brings into question the experimental determinations of the astrophysically important (n,gamma) cross sections for short-lived radioactive targets.
Timofeyuk NK, Thompson IJ (2008) Spectroscopic factors and asymptotic normalization coefficients in mirror three-body systems, Physical Review C - Nuclear Physics 78 (5) 054322 pp. 1-10
Using a three-body model, we study the dependence of spectroscopic factors for the overlap integrals )core+N|core+N+N* on the binding energy of the core +?N subsystem, considering as prototypes 6He, 6Be, 9Li, 9C, 18O, and 18Ne. We show that at small N-core binding energies these spectroscopic factors can be strongly influenced by the geometrical mismatch between the two-body N-core wave function that stretches into the classically forbidden region and the spatially confined three-body function. This mismatch comes from the strong two-body correlations between the nucleons outside the core and due to the core recoil effects. The mismatch leads to symmetry breaking in mirror spectroscopic factors that in some cases can be large enough to be observed in nucleon removal reactions. It is also responsible for deviations of the ratios of mirror asymptotic normalization coefficients (ANCs) from the simple model-independent analytical estimates. We discuss the influence of such mirror symmetry breaking on the prediction of direct stellar (p,³) reactions from the measured mirror neutron ANCs.
Matta A, Beaumel D, Otsu H, Lapoux V, Timofeyuk NK, Aoi N, Assie M, Baba H, Boissinot S, Chen RJ, Delaunay F, de Sereville N, Franchoo S, Gangnant P, Gibelin J, Hammache F, Houarner C, Imai N, Kobayashi N, Kubo T, Kondo Y, Kawada Y, Khiem LH, Kurata-Nishimura M, Kuzmin EA, Lee J, Libin JF, Motobayashi T, Nakamura T, Nalpas L, Nikolskii EY, Obertelli A, Pollacco EC, Rindel E, Rosier P, Saillant F, Sako T, Sakurai H, Sanchez-Benitez AM, Scarpaci J-A, Stefan I, Suzuki D, Takahashi K, Takechi M, Takeuchi S, Wang H, Wolski R, Yoneda K (2015) New findings on structure and production of He-10 from Li-11 with the (d,He-3) reaction,PHYSICAL REVIEW C 92 (4) ARTN 041302 AMER PHYSICAL SOC
Kievsky A, Gattobigio M, Timofeyuk NK (2013) Efimov Spectrum in Bosonic Systems with Increasing Number of Particles, Few-Body Systems pp. 1-4
It is well-known that three-boson systems show the Efimov effect when the two-body scattering length a is large with respect to the range of the two-body interaction. This effect is a manifestation of a discrete scaling invariance (DSI). In this work we study DSI in the N-body system by analysing the spectrum of N identical bosons obtained with a pairwise gaussian interaction close to the unitary limit. We consider different universal ratios such as {Mathematical expression} and {Mathematical expression}, with {Mathematical expression} being the energy of the ground (i = 0) and first-excited (i = 1) state of the system, for {Mathematical expression}. We discuss the extension of the Efimov radial law, derived by Efimov for N = 3, to general N. © 2013 Springer-Verlag Wien.
© 2015 American Physical Society. This paper presents a numerical convergence study of a hyperspherical-harmonics expansion for binding energies of a system of 4dNd728 helium atoms using a phenomenological soft attractive two-body He-He potential and a repulsive three-body force aimed at compensating for the absence of the two-body repulsive core. Earlier calculations with such a potential have shown an improved convergence when N increases from four to six. The present study reveals that the improved convergence occurs only for a limited range of N determined by the range of the three-body repulsion. For a soft repulsive three-body force, the convergence is fast for Nd20, while for a short-range three-body repulsion it deteriorates at Ne10. The reasons for this deterioration are discussed. The range of the three-body force also determines the binding energy behavior with N, and it is also responsible for binding the excited states. The long-range force binds all first excited 0+ states but strongly underbinds the systems of N helium atoms at large N. The short-range force does not bind the first 0+ states for Ad7 but gives better predictions of binding energies as compared to the calculations of other authors though overestimating them. Some options to improve both the description of the binding energies and the convergence of the hyperspherical-harmonics expansion using phenomenological forces are discussed. It is pointed out that a fast convergence is very much needed for the reliable predictions of states with nonzero angular momentum, examples of which are also given.
Tengborn E, Moro AM, Nilsson T, Alcorta M, Borge MJG, Cederkäll J, Diget C, Fraile LM, Fynbo HOU, Gomez-Camacho J, Jeppesen HB, Johansson HT, Jonson B, Kirsebom OS, Knudsen HH, Madurga M, Nyman G, Richter A, Riisager K, Schrieder G, Tengblad O, Timofeyuk N, Turrion M, Voulot D, Wenander F (2011) The 8Li + 2H reaction studied in inverse kinematics at 3.15 MeV/nucleon using the REX-ISOLDE post-accelerator,Physical Review C - Nuclear Physics 84 (6)
The reaction 8Li + 2H has been studied in inverse kinematics at the incident energy of 3.15 MeV/nucleon, using the REX-ISOLDE post-accelerator. The reaction channels corresponding to (d,p), (d,d), and (d,t) reactions populating ground states and low-lying excited states in 7 -9Li have been identified and the related angular distributions extracted and compared with coupled-channels, distorted-wave Born approximation (DWBA), and coupled-reaction-channels calculations. For the inelastic and (d,t) channels we find that higher order effects are very important and hence one needs to go beyond the simple DWBA to extract reliable structure information from these processes. © 2011 American Physical Society.
Timofeyuk NK, Descouvemont P (2005) Asymptotic normalization coefficients for mirror virtual nucleon decays
in a microscopic cluster model
,
Phys.Rev.C 71 pp. 064305-064305
It has been suggested recently (Phys. Rev. Lett. 91, 232501 (2003)) that
charge symmetry of nucleon-nucleon interactions relates the Asymptotic
Normalization Coefficients (ANCs) of proton and neutron virtual decays of
mirror nuclei. This relation is given by a simple analytical formula which
involves proton and neutron separation energies, charges of residual nuclei and
the range of their strong interaction with the last nucleon. Relation between
mirror ANCs, if understood properly, can be used to predict astrophysically
relevant direct proton capture cross sections using neutron ANCs measured with
stable beams. In this work, we calculate one-nucleon ANCs for several light
mirror pairs, using microscopic two-, three- and four-cluster models, and
compare the ratio of mirror ANCs to the predictions of the simple analytic
formula. We also investigate mirror symmetry between other characteristics of
mirror one-nucleon overlap integrals, namely, spectroscopic factors and
single-particle ANCs.
It has been suggested recently ({\it Phys. Rev. Lett.} 91, 232501 (2003))
that the widths of narrow proton resonances are related to neutron Asymptotic
Normalization Coefficients (ANCs) of their bound mirror analogs because of
charge symmetry of nucleon-nucleon interactions.
This relation is approximated by a simple analytical formula which involves
proton resonance energies, neutron separation energies, charges of residual
nuclei and the range of their strong interaction with the last nucleon. In the
present paper, we perform microscopic-cluster model calculations for the ratio
of proton widths to neutron ANCs squared in mirror states for several light
nuclei. We compare them to predictions of the analytical formula and to
estimates made within a single-particle potential model. A knowledge of this
ratio can be used to predict unknown proton widths for very narrow low-lying
resonances in the neutron-deficient region of the $sd$- and $pf$-shells, which
is important for understanding the nucleosynthesis in the $rp$-process.
Timofeyuk NK, Descouvemont P, Thompson IJ (2008) Threshold effects in the 27P(32+)’26Si+p and 27Mg(32+)’26Mg+n mirror decays and the stellar reaction 26Si(p,³)27P, Physical Review C - Nuclear Physics 78 (4) 044323 pp. 1-9
Timofeyuk NK (2015) Widths of low-lying nucleon resonances in light nuclei in the source-term approach, PHYSICAL REVIEW C 92 (3) ARTN 034330 AMER PHYSICAL SOC
Timofeyuk NK (2003) Do multineutrons exist?,J.Phys. G 29 pp. L9-L9
Following recent work in which events which may correspond to a bound
tetraneutron ($^4$n) were observed, it is pointed out that from the theoretical
perspective the two-body nucleon-nucleon (NN) force cannot by itself bind four
neutrons, even if it could bind a dineutron. Unrealistic modifications of the
NN force or introduction of unreaslistic four-nucleon force would be needed in
order to bind the tetraneutron. The existence of other multineutron systems is
discussed.
Timofeyuk NK (2007) Long-range behavior of valence nucleons in a hyperspherical formalism, PHYSICAL REVIEW C 76 (4) ARTN 044309
Timofeyuk NK (2002) On the existence of a bound tetraneutron,
Following recent work in which events which may correspond to a bound
tetraneutron ($^4$n) were observed, it is pointed out that from the theoretical
perspective the two-body nucleon-nucleon force cannot by itself bind four
neutrons, even if it can bind a dineutron.
A very strong phenomenological four-nucleon (4N) force is needed in order to
bind the tetraneutron. Such a 4N force, if it existed, would bind $^4$He by
about 100 MeV. Alternative experiments such as ($^8$He,$^4$n) are proposed to
search for the tetraneutron.
Mukha I, Suemmerer K, Acosta L, Alvarez MAG, Casarejos E, Chatillon A, Cortina-Gil D, Egorova IA, Espino JM, Fomichev A, Garcia-Ramos JE, Geissel H, Gomez-Camacho J, Grigorenko L, Hofmann J, Kiselev O, Korsheninnikov A, Kurz N, Litvinov YA, Litvinova E, Martel I, Nociforo C, Ott W, Pfuetzner M, Rodriguez-Tajes C, Roeckl E, Stanoiu M, Timofeyuk NK, Weick H, Woods PJ (2010) Spectroscopy of proton-unbound nuclei by tracking their decay products in-flight: One- and two-proton decays of F-15, Ne-16, and Na-19, PHYSICAL REVIEW C 82 (5) ARTN 054315
Timofeyuk NK, Descouvemont P, Thompson IJ (2008) Threshold effects in the P-27(3/2+)-> Si-26+p and Mg-27(3/2+)-> Mg-26+n mirror decays and the stellar reaction Si-26(p,gamma)P-27, PHYSICAL REVIEW C 78 (4) ARTN 044323
Fomichev AS, Ter-Akopian GM, Chudoba V, Daniel AV, Golovkov MS, Gorshkov VA, Grigorenko LV, Krupko SA, Oganessian YT, Sidorchuk SI, Slepnev RS, Stepantsov SV, Ershov SN, Lukyanov VK, Danilin BV, Korsheninnikov AA, Goldberg VZ, Pfützner M, Mukha IG, Simon H, Tarasov OB, Timofeyuk NK, Zhukov MV, Lawrie K, Newman RT (2010) The suggested new fragment separator acculinna-2, Acta Physica Polonica B 41 (2) pp. 475-480
We present new project of fragment separator ACCULINNA-2 that is being planned to be constructed in Flerov Laboratory of Nuclear Reaction, JINR. The ACCULINNA-2 facility is not intended to compete with the new large in-flight RIB facilities. It should complement the existing/constructed facilities in certain fields. Namely, ACCULINNA-2 should provide high intensity RIBs in the lowest energy range attainable for in-flight separators.
Timofeyuk NK, Johnson RC, Mukhamedzhanov AM (2006) Erratum: Relation between proton and neutron asymptotic normalization coefficients for light mirror nuclei and its relevance to nuclear astrophysics (Physical Review Letters (2003) 91 (232501)), Physical Review Letters 97 (6)
Trache L, Azhari A, Carstoiu F, Clark HL, Gagliardi CA, Lui YW, Mukhamedzhanov AM, Tang X, Timofeyuk N, Tribble RE (2003) Asymptotic normalization coefficients for B-8 -> Be-7+p from a study of Li-8 -> Li-7+n,PHYSICAL REVIEW C 67 (6) ARTN 062801 AMER PHYSICAL SOC
Kievsky A, Gattobigio M, Timofeyuk N (2014) Efimov Spectrum in Bosonic Systems with Increasing Number of Particles,Few-Body Systems 55 (8-10) pp. 945-948 Springer
It is well-known that three-boson systems show the Efimov effect when the two-body scattering length a is large with respect to the range of the two-body interaction. This effect is a manifestation of a discrete scaling invariance (DSI). In this work we study DSI in the N-body system by analysing the spectrum of N identical bosons obtained with a pairwise gaussian interaction close to the unitary limit. We consider different universal ratios such as EN 0/E3 0 and EN 1/EN 0, with EN i being the energy of the ground (i = 0) and first-excited (i = 1) state of the system, for N d 16. We discuss the extension of the Efimov radial law, derived by Efimov for N = 3, to general N. © 2013 Springer-Verlag Wien.
Waldecker S, Timofeyuk N (2016) Implications for (d,p) reaction theory from nonlocal dispersive optical model analysis of Ca40(d,p)Ca41,Physical Review C: Nuclear Physics 94 (3) 034609 American Physical Society
The nonlocal dispersive optical model (NLDOM) nucleon potentials are used for the first time in the adiabatic analysis of a (d,p) reaction to generate distorted waves both in the entrance and exit channels. These potentials have been designed and fitted in [Phys. Rev. Lett. 112, 162502 (2014)] to constrain relevant single-particle physics in a consistent way by imposing the fundamental properties, such as nonlocality, energy-dependence and dispersive relations, that follow from the complex nature of nuclei. However, the NLDOM prediction for the 40Ca(d,p)41Ca cross sections at low energy, typical for some modern radioactive beam ISOL facilities, is about 70% higher than the experimental data despite being reduced by the NLDOM spectroscopic factor of 0.73. This overestimation comes most likely either from insufficient absorption or due to constructive interference between ingoing and outgoing waves. This indicates strongly that additional physics arising from many-body effects is missing in the widely used current versions of (d,p) reaction theories.
Bailey GW, Timofeyuk Natalia, Tostevin Jeffrey (2017) Nonlocal nucleon-nucleus interactions in (d,p) reactions: Role of the deuteron D state,Physical Review C: Nuclear Physics 95 (2) 024603 American Physical Society
Theoretical models of the (d, p) reaction are exploited for both nuclear astrophysics and spectroscopic studies in nuclear physics. Usually, these reaction models use local optical model potentials to describe the nucleon- and deuteron-target interactions. Within such a framework the importance of the deuteron D-state in low-energy reactions is normally associated with spin observables and tensor polarization effects - with very minimal influence on differential cross sections. In contrast, recent work that includes the inherent nonlocality of the nucleon optical model potentials in the Johnson-Tandy adiabatic-model description of the (d, p) transition amplitude, which accounts for deuteron break-up effects, shows sensitivity of the reaction to the large n-p relative momentum content of the deuteron wave function. The dominance of the deuteron D-state component at such high momenta leads to significant sensitivity of calculated (d, p) cross sections and deduced spectroscopic factors to the choice of deuteron wave function [Phys. Rev. Lett. 117, 162502 (2016)]. We present details of the Johnson-Tandy adiabatic model of the (d, p) transfer reaction generalized to include the deuteron D-state in the presence of nonlocal nucleon-target interactions. We present exact calculations in this model and compare these to approximate (leading-order) solutions. The latter, approximate solutions can be interpreted in terms of local optical potentials, but evaluated at a shifted value of the energy in the nucleon-target system. This energy shift is increased when including the D-state contribution. We also study the expected dependence of the D-state effects on the separation energy and orbital angular momentum of the transferred nucleon. Their influence on the spectroscopic information extracted from (d, p) reactions is quantified for a particular case of astrophysical significance.
Timofeyuk N, Johnson RC (2013) Nonlocality in the adiabatic model of A(d, p)B reactions,PHYSICAL REVIEW C 87 (6) ARTN 0 AMER PHYSICAL SOC
In a previous publication [Phys. Rev. Lett. 110, 112501 (2013)] we have proposed a generalization of the adiabatic model of (d,p) reactions that allows the nonlocality of the nucleon optical potential to be included in a consistent way together with the deuteron breakup. In this model an effective local d?A potential is constructed from local nucleon optical potentials taken at an energy shifted by
Timofeyuk N (2010) Overlap functions, spectroscopic factors, and asymptotic normalization coefficients generated by a shell-model source term,Physical Review C - Nuclear Physics 81 (6) 064306 pp. 1-21 American Physical Society
Overlap functions for one-nucleon removal are calculated as solutions of the inhomogeneous equation. The source term for this equation is generated by the 0?É no-core shell-model wave functions and the effective nucleon-nucleon (NN) interactions that fit oscillator matrix elements derived from the NN scattering data. For the lightest A}4 nuclei this method gives reasonable agreement with exact ab initio calculations. For 4
Pang DY, Timofeyuk Natalia, Johnson Ronald, Tostevin Jeffrey (2013) Rapid convergence of the Weinberg expansion of the deuteron stripping amplitude,Physical Review C: Nuclear Physics 87 064613
Theories of (d,p) reactions frequently use a formalism based on a transition amplitude that is dominated by the components of the total three-body scattering wave function where the spatial separation between the incoming neutron and proton is confined by the range of the n-p interaction, Vnp. By comparison with calculations based on the continuum discretized coupled channels method we show that the (d,p) transition amplitude is dominated by the first term of the expansion of the three-body wave function in a complete set of Weinberg states. We use the 132Sn(d,p)133Sn reaction at 30 and 100 MeV as examples of contemporary interest. The generality of this observed dominance and its implications for future theoretical developments are discussed.
Timofeyuk N (2013) Spectroscopic factors and asymptotic normalization coefficients for 0p-shell nuclei: Recent updates,Physical Review C: Nuclear Physics 88 044315 American Physical Society
Extended tables are presented for spectroscopic factors, asymptotic normalization coefficients and rms radii
of one-nucleon overlap functions for 0p-shell nuclei calculated in the source term approach using shell model
wave functions. The tabulated data includes both new results and updates on previously published values. They
are compared with recent results obtained in ab initio calculations, and with experimental data, where available.
The reduction of spectroscopic factors with respect to traditional shell model values as well as its neutron-proton
asymmetry is also discussed
Mukha I, Sümmerer K, Acosta L, Alvarez MAG, Casarejos E, Chatillon A, Cortina-Gil D, Egorova IA, Espino JM, Fomichev A, García-Ramos JE, Geissel H, Gómez-Camacho J, Grigorenko L, Hofmann J, Kiselev O, Korsheninnikov A, Kurz N, Litvinov YA, Litvinova E, Martel I, Nociforo C, Ott W, Pfützner M, Rodríguez-Tajes C, Roeckl E, Stanoiu M, Timofeyuk Natalia, Weick H, Woods PJ (2010) Spectroscopy of proton-unbound nuclei by tracking their decay products in-flight: One- and two- proton decays of F15, Ne16, and Na19,Physical Review C - Nuclear Physics 82 (5) 054315 pp. 1-14 American Physical Society
A powerful method of investigating proton-unbound nuclear states by tracking their decay products in flight is discussed in detail. To verify the method, four known levels in
15
F
,
16
Ne
, and
19
Na
were investigated by measuring the angular correlations between protons and the respective heavy-ion fragments stemming from the precursor decays in flight. The parent nuclei of interest were produced in nuclear reactions of one-neutron removal from
17
Ne
and
20
Mg
projectiles at energies of 410?450
A
MeV. The trajectories of the respective decay products,
14
O

+
p
+
p and
18
Ne

+
p
+
p, were measured by applying a tracking technique with microstrip detectors. These data were used to reconstruct the angular correlations of the fragments, which provided information on energies and widths of the parent states. In addition for reproducing properties of known states, evidence for hitherto unknown excited states in
15
F
and
16
Ne
was found. This tracking technique has an advantage in studies of exotic nuclei beyond the proton drip line measuring the resonance energies and widths with a high precision although by using low-intensity beams and very thick targets.

Timofeyuk N, Thompson I, Tostevin JA (2008) Single-particle motion at large distances in 2N+core cluster systems near the drip line: a challenge for nuclear theory and experiment,Journal of Physics: Conference Series 111 (1) 012034
There exists a class of nuclei that are obtained by adding one nucleon to a loosely-bound nucleon-core system, for example $^{12}$Be, $^9$C, $^{18}$Ne. For such nuclei, one-nucleon overlap integrals that represent single-particle motion can strongly differ from the standard ones due to the correlations between the two nucleons above the core. The possible non-standard overlap behaviour should be included in the interpretation of the experimental data derived from one nucleon removal reactions such as knockout, transfer and breakup, as well as the predictions of low-energy nucleon capture that leads to these nuclei. We investigate the non-standard behaviour within a three-body model and discuss the challenges associated with this problem.
Bailey G, Timofeyuk N, Tostevin J (2016) Sensitivity of (d,p) reactions to high n-p momenta and the consequences for nuclear spectroscopy studies,Physical Review Letters 117 (16) 162502 American Physical Society
Theoretical models of low-energy (d,p) single-neutron transfer reactions are a crucial link between experimentation, nuclear structure and nuclear astrophysical studies. Whereas reaction models that use local optical potentials are insensitive to short-range physics in the deuteron, we show that including the inherent nonlocality of the nucleon-target interactions and realistic deuteron wave functions generates significant sensitivity to high n-p relative momenta and to the underlying nucleon-nucleon interaction. We quantify this effect upon the deuteron channel distorting potentials within the framework of the adiabatic deuteron breakup model. The implications for calculated (d,p) cross sections and spectroscopic information deduced from experiments are discussed.
Kievsky A., Polls A., Juliá Díaz B., Timofeyuk Natalia (2017) Saturation properties of helium drops from a leading-order description,Physical Review A 96 (4) pp. 040501-1 American Physical Society
Saturation properties are directly linked to the short-range scale of the two-body interaction of the particles. The case of helium is particular, from one hand the two-body potential has a strong repulsion at short distances. On the other hand, the extremely weak binding of the helium dimer locates this system very close to the unitary limit allowing for a description based on an effective theory. At leading order of this theory a two- and a three-body term appear, each one characterized by a low energy constant. In a potential model this description corresponds to a soft potential model with a two-body term purely attractive plus a three-body term purely repulsive constructed to describe the dimer and trimer binding energies. Here we analyse the capability of this model to describe the saturation properties making a direct link between the low energy scale and the short-range correlations. We will show that the energy per particle, E_N/N, can be obtained with reasonable accuracy at leading order extending the validity of this approximation, characterizing universal behavior in few-boson systems close to the unitary limit, to the many-body system.
Timofeyuk N. K. (2018) Three-nucleon force contribution in the distorted-wave theory of (d,p) reactions,Physical Review C 97 (5) 054601 pp. 054601-1 American Physical Society
The distorted-wave theory of
A
(
d
,
p
)
B
reactions, widely used to analyze experimental data, is based on a Hamiltonian that includes only two-nucleon interactions. However, numerous studies of few-nucleon systems and many modern developments in nuclear structure theory show the importance of the three-nucleon (
3
N
) force. The purpose of this paper is to study the contribution of the
3
N
force of the simplest possible form to the
A
(
d
,
p
)
B
reaction amplitude. This contribution is given by a new term that accounts for the interaction of the neutron and proton in the incoming deuteron with one of the target nucleons. This term involves a new type of nuclear matrix elements containing an infinite number of target excitations in addition to the main part associated with the traditional overlap function between
A
and
B
. The nuclear matrix elements are calculated for double-closed shell targets within a mean field theory where target excitations are shown to be equivalent to exchanges between valence and core nucleons. These matrix elements can be readily incorporated into available reaction codes if the
3
N
interaction has a spin-independent zero-range form. Distorted-wave calculations are presented for a contact
3
N
force with the volume integral fixed by the chiral effective field theory at the next-to-next-to-leading order. For this particular choice, the
3
N
contribution is noticeable, especially at high deuteron incident energies. No
3
N
effects are seen for incident energies below the Coulomb barrier. The finite range can significantly affect the
3
N
contribution to the
(
d
,
p
)
cross sections. Finite-range studies require new formal developments and, therefore, their contribution is preliminarily assessed within the plane-wave Born approximation, together with sensitivity to the choice of the deuteron model.
Gómez-Ramos M., Timofeyuk N. K. (2018) Reduced sensitivity of the (d,p) cross sections to the deuteron model beyond the adiabatic approximation,Physical Review C 98 (1) 011601(R) pp. 011601-1 - 011601-6 American Physical Society
It has recently been reported [Phys. Rev. Lett. 117, 162502 (2016)] that (d, p) cross sections
can be very sensitive to the n-p interactions used in the adiabatic treatment of deuteron breakup
with nonlocal nucleon-target optical potentials. To understand to what extent this sensitivity could
originate in the inaccuracy of the adiabatic approximation we have developed a leading-order local-equivalent continuum-discretized coupled-channel model that accounts for non-adiabatic effects in
the presence of nonlocality of nucleon optical potentials. We have applied our model to the astro-physically relevant reaction 26mAl(d, p) 27Al using two different n-p potentials associated with the
lowest and the highest n-p kinetic energy in the short-range region of their interaction, respectively.
Our calculations reveal a significant reduction of the sensitivity to the high n-p momenta thus confirming that it is mostly associated with theoretical uncertainties of the adiabatic approximation
itself. The non-adiabatic effects in the presence of nonlocality were found to be stronger than those
in the case of the local optical potentials. These results argue for extending the analysis of the (d, p)
reactions, measured for spectroscopic studies, beyond the adiabatic approximation.
Berry T.A., Podolyak Zs., Carroll R.J., Lic? R., Grawe H., Timofeyuk N.K., Alexander T., Andreyev A.N., Ansari S., Borge M.J.G., Creswell J., Fahlander C., Fraile L.M., Fynbo H.O.U., Gelletly W., Gerst R.-B., Górska M., Gredley A., Greenlees P., Harkness-Brennan L.J., Huyse M., Judge S.M., Judson D.S., Konki J., Kurcewicz J., Kuti I., Lalkovski S., Lazarus I., Lund M., Madurga M., M?rginean N., M?rginean R., Marroquin I., Mihai C., Mihai R.E., Nácher E., Nae S., Negret A., Nic? C., Page R.D., Pascu S., Patel Z., Perea A., Pucknell V., Rahkila P., Rapisarda E., Regan P.H., Rotaru F., Shand C.M., Simpson E.C., Sotty Ch., Stegemann S., Stora T., Tengblad O., Turturica A., Van Duppen P., Vedia V., Wadsworth R., Walker P.M., Warr N., Wearing F., De Witte H. (2019) Investigation of the ”n = 0 selection rule in Gamow-Teller transitions: The ²-decay of 207Hg,Physics Letters B 793 pp. 271-275 Elsevier
Gamow-Teller ² decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This ”n=0 requirement plays a major role in the ² decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z=50 (for N à 82) and Z = 82 (for N à 126). The level of forbiddenness of the ”n=1v1g9/2 ’ À0g7/2 transition has been investigated from the ² decay of the ground state of 207Hg into the single-proton-hole nucleus 207Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible ³-ray transitions depopulating the À0g-17/2 state in 207Tl, an upper limit of 3.9 x 10-3% was obtained for the probability of this decay, corresponding to log ft à 8.8 within a 95% confidence limit. This is the most stringent test of the ”n=0 selection rule to date.
Gómez-Ramos M, Timofeyuk N K (2019) Perey-effect in continuum-discretized coupled-channel description of (d, p) reactions,Journal of Physics G: Nuclear and Particle Physics 46 085102 pp. 1-12 IOP Publishing
The Perey effect in two-body channels of (d, p) reactions has been known for a long time. It arises when the nonlocal two-body deuteron-target and/or proton-target problem is approximated by a local one, manifesting itself in a reduction of the scattering channel wave functions in the nuclear interior. However, the (d, p) reaction mechanism requires explicit accounting for three-body dynamics involving the target and the neutron and proton in the deuteron. Treating nonlocality of the nucleon-target interactions within a three-body context requires significant effort and demands going beyond the widely-used adiabatic approximation, which can be done using a continuum-discretized coupled-channel (CDCC) method. However, the inclusion of nonlocal interactions into the CDCC description of (d, p) reactions has not been developed yet. Here, we point out that, similarly to the two-body nonlocal case, nonlocality in a three-body channel can be accounted for by introducing the Perey factors. We explain this procedure and present the first CDCC calculations to our knowledge including the Perey effect.
Timofeyuk N K (2019) Three-body problem with velocity-dependent optical potentials: a case of (d, p) reactions,Journal of Physics G: Nuclear and Particle Physics 46 (6) IOP Publishing
The change in mass of a nucleon, arising from its interactions with other nucleons inside the target, results in velocity-dependent terms in the Schrödinger equation that describes nucleon scattering. It has recently been suggested in a number of publications that introducing and fitting velocity-dependent terms improves the quality of the description of nucleon scattering data for various nuclei. The present paper discusses velocity-dependent optical potentials in the context of a three-body problem used to account for deuteron breakup in the entrance channel of (d, p) reactions. Such potentials form a particular class of nonlocal optical potentials which are a popular object of modern studies. It is shown here that because of a particular structure of the velocity-dependent terms the three-body problem can be formulated in two different ways. Solving this problem within an adiabatic approximation results in a significant difference between the two approaches caused by contributions from the high n?p momenta in deuterons in one of them. Solving the three-body problem beyond the adiabatic approximation may remove such contributions, which is indirectly confirmed by replacing the adiabatic approximation by the folding Watanabe model where such contributions are suppressed. Discussion of numerical results is carried out for the 40Ca(d, p)41Ca reaction where experimental data both on elastic scattering in entrance and exit channels and on nucleon transfer are available.
Dinmore M. J., Timofeyuk N. K., Al-Khalili J. S., Johnson R. C. (2019) Effects of an induced three-body force in the incident channel of (d,p) reactions,Physical Review C 99 (6) 064612 pp. 064612-1 American Physical Society
A widely accepted practice for treating deuteron breakup in A(d,p)B reactions relies on solving a three-body A+n+p Schrödinger equation with pairwise A?n, A?p and n?p interactions. However, it was shown in Phys. Rev. C 89, 024605 (2014) that projection of the many-body A+2 wave function into the three-body A+n+p channel results in a complicated three-body operator that cannot be reduced to a sum of pairwise potentials. It contains explicit contributions from terms that include interactions between the neutron and proton via excitation of the target A. Such terms are normally neglected. We estimate the first-order contribution of these induced three-body terms and show that applying the adiabatic approximation to solving the A+n+p model results in a simple modification of the two-body nucleon optical potentials. We illustrate the role of these terms for the case of 40Ca(d,p)41Ca transfer reactions at incident deuteron energies of 11.8, 20, and 56 MeV, using several parametrizations of nonlocal optical potentials.
Timofeyuk N.K., Johnson R.C. (2020) Theory of deuteron stripping and pick-up reactions for nuclear structure studies,Progress in Particle and Nuclear Physics 111 103738 Elsevier
Deuteron stripping and pick-up experiments - (d; p) and (p; d) - have been used for a long time
to study the structure of nuclei. Today these experiments are often carried out in inverse kinematics in state-of-the-art radioactive beams facilities around the world, extending the boundaries of
our knowledge of the nuclear chart. The nuclear structure information obtained from these experiments relies entirely on transfer reaction theory. We review the theory of (d; p) and (p; d) reactions
starting from early formulations and ending with the most recent developments. In particular,
we describe the recent progress made in the understanding of the three-body dynamics associated
with the deuteron breakup degrees of freedom, including effects of nonlocality, and discuss the
role of many-body degrees of freedom within the three-body context. We also review advances
in structure model calculations of one-nucleon overlap functions - an important structure input
to (d; p) and (p; d) reaction calculations. We emphasize the physics missing in widely-used standard approaches available to experimentalists and review ideas and efforts aimed at including this
physics, formulating the crucial tasks for further development of deuteron stripping and pickup
reaction theory
Berry T. A., Podolyak Zs., Carroll R. J., Lic? R., Brown B. A., Grawe H., Sotty Ch., Timofeyuk N. K., Alexander T., Andreyev A. N., Ansari S., Borge M. J. G., Brunet M., Cresswell J. R., Fahlander C., Fraile L. M., Fynbo H. O. U., Gamba E., Gelletly W., Gerst R.-B., Górska M., Gredley A., Greenlees P., Harkness-Brennan L. J., Huyse M., Judge S. M., Judson D. S., Konki J., Kowalska M., Kurcewicz J., Kuti I., Lalkovski S., Lazarus I., Lund M., Madurga M., M?rginean N., M?rginean R., Marroquin I., Mihai C., Mihai R. E., Nácher E., Negret A., Nae S., Nic? C., Pascu S., Page R. D., Patel Z., Perea A., Phrompao J., Piersa M., Pucknell V., Rahkila P., Rapisarda E., Regan P. H., Rotaru F., Rudigier M., Shand C. M., Shearman R., Simpson E. C., Stegemann S., Stora T., Tengblad O., Turturica A., Van Duppen P., Vedia V., Walker P. M., Warr N., Wearing F. P., De Witte H. (2020) Octupole states in 207Tl studied through ² decay,Physical Review C 101 (5) 054311 American Physical Society
The ² decay of 207Hg
into the single-proton-hole nucleus 207Tl
has been studied through ³-ray spectroscopy at the ISOLDE Decay Station (IDS) with the aim of identifying states resulting from coupling of the Às?11/2, Àd?13/2, and Àh?111/2 shell model orbitals to the collective octupole vibration. Twenty-two states were observed lying between 2.6 and 4.0 MeV, eleven of which were observed for the first time, and 78 new transitions were placed. Two octupole states (s1/2-coupled) are identified and three more states (d3/2-coupled) are tentatively assigned using spin-parity inferences, while further h11/2-coupled states may also have been observed for the first time. Comparisons are made with state-of-the-art large-scale shell model calculations and previous observations made in this region, and systematic underestimation of the energy of the octupole vibrational states is noted. We suggest that in order to resolve the difference in predicted energies for collective and noncollective t=1
states (t is the number of nucleons breaking the 208Pb core), the effect of t=2 mixing may be reduced for octupole-coupled states. The inclusion of mixing with t=0,2,3 excitations is necessary to replicate all t=1 state energies accurately.