Dr Iain Lee
Academic and research departments
Theoretical Nuclear Physics Group, School of Mathematics and Physics.About
My research project
Quantum dynamics in dense stellar plasmaI will be using density matrix dynamics of an open quantum system to measure nuclear fusion reaction rates in dense stellar plasma. Including different environmental effects due to the plasma, such as competing atomic and nuclear processes, will hopefully provide interesting information on quantum tunnelling probabilities and be useful in the ongoing efforts to understand the origin of chemical elements.
I will be using density matrix dynamics of an open quantum system to measure nuclear fusion reaction rates in dense stellar plasma. Including different environmental effects due to the plasma, such as competing atomic and nuclear processes, will hopefully provide interesting information on quantum tunnelling probabilities and be useful in the ongoing efforts to understand the origin of chemical elements.
Publications
Using a classical dynamical reaction model, angular momentum (L) values of a compound nucleus due to incomplete fusion at energies near and above the Coulomb barrier are studied. In this model, a projectile consisting of two cluster nuclei is fired at a stationary target nucleus. After breakup of the projectile due to Coulombic and nuclear forces, an α-cluster fuses with a 208Pb target, forming an excited 212Po compound nucleus. Results show that all incomplete fusion reactions produced higher angular momentum in the compound nucleus compared to a direct beam of α particles at the same incident energy. The highest angular momentum values produced in 212Po for near and above Coulomb barrier energies were obtained using a 20Ne projectile, at 16 \hbar and 40 \hbar, respectively. This produced 25% and 50% L values above the next highest-Z projectile used, 8Be, respectively.
The quantum dynamics of a particle in a one-dimensional box with an oscillating wall (the Fermi accelerator) is investigated. The model is applied to the motion of a single nucleon in the mean-field potential of a heavy atomic nucleus whose surface vibrates. By directly solving the time-dependent Schrödinger equation, both the state of the particle and its mean-energy are studied. The effects of the frequency of the wall oscillation on the nucleon’s energy are addressed. Its energy oscillates in phase with the moving wall for all frequencies, showing no chaotic behaviour. There is a large initial peak of the nucleon’s energy as the particle adjusts to the sudden change in the size of the box and a varying relaxation time as it plateaus towards lower energy and a partial equilibrium. Small oscillations in energy continue, since there cannot be a true equilibrium while the wall is moving. The quantum coherence between the different parts of the nucleon’s wave-function in real space is very much preserved. This research lays the foundation for future investigations into quantum tunnelling in the Fermi accelerator.