### Dr Alexis Diaz Torres

### Biography

I grew up in rural Cuba and was in the Cuban Team at the 19th International Junior Physics Olympiad in Bad Ischl (Austria) in 1988. I studied Physics at KLTE (Hungary), InSTEC (Cuba) and JLU in Giessen (Germany), with research experience at Surrey (UK), Frankfurt-U (Germany), ANU (Australia) and ECT* (Italy). My scientific interests include the physics of nuclear reactions, which is crucial for a better comprehension of element creation in the universe and is therefore at the core of science programmes at new generation facilities.

### Areas of specialism

### University roles and responsibilities

- Leader of the Math & Physics Programmes
- Module Leader of Mathematical and Computational Physics (PHY1038)

### Research

### Research interests

These include Nuclear Theory; Few-Body & Many-Body Physics; Quantum Dynamics; Theory of Open Quantum Systems; Nuclear Molecules; Super-Heavy Elements Research; Nuclear Astrophysics.

- *OWL: a code for the two-center shell model with spherical Woods-Saxon potentials*, A. Diaz-Torres, Computer Physics Communications **224** (2018) 381-386.

- *PLATYPUS: a code for reaction dynamics of weakly bound nuclei at near-barrier energies within a classical dynamical model*, A. Diaz-Torres, Computer Physics Communications **182** (2011) 1100-1104.

### My teaching

I am currently lecturing the Mathematical and Computational Physics module (PHY1038) in Semester 2 for year-1 students. I am also teaching the Modern Computational Techniques module (PHY3042) in Semester 1 for year-3 students, as well as Computer Lab Projects of the modules PHY2071/73 in Semester 2 for year-2 students. Other teaching activities include small group tutorials in Semester 1 and the supervision of both BSc Final Year Projects (PHY3002) in Semester 2 and MSc Physics Dissertation Projects (PHYM021) over the summer.

Linking teaching and research, a BSc final year project turned into a peer-reviewed article: Diaz-Torres & Quraishi, PRC 97 (2018) 024611.

### Supervision

# Postgraduate research supervision

**Former PhD students (as primary supervisor):**

- Dr. Maddalena Boselli (ECT* & Trento U). The thesis can be downloaded from http://eprints-phd.biblio.unitn.it/1852/

**Current PhD students (as primary supervisor):**

- Terence Vockerodt, Rafael Van den Bossche

They are working on challenging research projects about reaction dynamics of complex atomic nuclei in slow collisions.

### My publications

### Highlights

Most of my publications can be downloaded from ResearchGate (https://www.researchgate.net/profile/Alexis_Diaz-Torres2). Please find below some ePrints at Surrey. A complete list of my publications can be found on ORCID (https://orcid.org/0000-0001-6234-9353).

### Publications

presented. The model is based on two spherical Wood-Saxon potentials and

the potential separable expansion method. It describes the single-particle

motion in low-energy nuclear collisions, and is useful for characterizing a

broad range of phenomena from fusion to nuclear molecular structures.

wave-packet dynamics, Physical Review C 97 (5) 055802 pp. 055802-1 - 055802-8 American Physical Society

Low-energy collisions are described in the body-fixed reference frame using wave-packet dynamics

within a nuclear molecular picture. A collective Hamiltonian drives the time propagation of the

wave-packet through the collective potential-energy landscape. The fusion imaginary potential for

specific dinuclear configurations is crucial for understanding the appearance of resonances in the

fusion cross section. The theoretical sub-barrier fusion cross sections explain some observed resonant

structures in the astrophysical S-factor. These cross sections monotonically decline towards

stellar energies. The structures in the data that are not explained are possibly due to cluster effects

in the nuclear molecule, which are to be included in the present approach.

A classical dynamical model that treats breakup stochastically is presented for low energy reactions of weakly bound nuclei. The three-dimensional model allows a consistent calculation of breakup, incomplete, and complete fusion cross sections. The model is assessed by comparing the breakup observables with continuum discretized coupled-channel quantum mechanical predictions, which are found to be in reasonable agreement. Through the model, it is demonstrated that the breakup probability of the projectile as a function of its distance from the target is of primary importance for understanding complete and incomplete fusion at energies near the Coulomb barrier.

A classical dynamical model that treats breakup stochastically is presented for low energy reactions of weakly bound nuclei. The three-dimensional model allows a consistent calculation of breakup, incomplete, and complete fusion cross sections. The model is assessed by comparing the breakup observables with continuum discretized coupled-channel quantum mechanical predictions, which are found to be in reasonable agreement. Through the model, it is demonstrated that the breakup probability of the projectile as a function of its distance from the target is of primary importance for understanding complete and incomplete fusion at energies near the Coulomb barrier.

_{12}C+

_{12}C is reported. Lowenergy

collisions are described in the body-fixed reference frame using wave-packet dynamics within a

nuclear molecular picture. In contrast to conventional methods, such as the potential model and the

coupled-channels approach, these new calculations reveal three resonant structures in the S-factor,

explaining some structures observed in the data. The structures in the data that are not explained are

possibly due to cluster effects in the nuclear molecule, which need to be included in the new approach.

^{184}Re from the

^{9}Be +

^{181}Ta reaction, Physical Review C 99 (5) 054617 pp. 054617-1 - 054617-6 American Physical Society

^{184}R in the incomplete fusion of the

^{9}Be +

^{181}Ta system were measured at

energies around the Coulomb barrier, using online activation followed by offline ³-ray spectroscopy method.

The PLATYPUS code that is based on a classical dynamical model is employed to analyze the measurements. By

applying a phenomenological approach, model calculation managed to fairly reproduce the order of magnitude

of the yield ratios at above barrier energies. Through the study, it is shown that the PLATYPUS code in conjunction

with a phenomenological analysis can provide a reasonable explanation of isomer yield ratios resulted from

incomplete fusion of weakly bound projectiles.