M.Sc Thesis

M.Sc StudentBar-Gill Nir
SubjectDynamics of a Lasing Atom in Hot Plasma
DepartmentDepartment of Physics
Supervisors PROFESSOR EMERITUS Amiram Ron
DR. Mordechai Botton


The research focuses on the temporal evolution of a lasing atom in hot plasma. Our objective is to derive evolution equations for the atomic populations and coherences. These equations are needed in the semi-classical model of the laser. We propose a novel approach, introducing a Hamiltonian for a lasing ion in hot plasma.  We model the plasma as an electron reservoir in thermal equilibrium, interacting through the Coulomb potential with lasing ions. The electron reservoir is described using the second quantization formalism, and the density matrix method is used to derive the Master Equation for the lasing ion. By eliminating the degrees of freedom of the reservoir, the evolution rates (transition for populations and dephasing for coherences) of the Master Equation are derived. The obtained expressions for the transition rates are in agreement with previously published results. The dephasing rates are composed of adiabatic and non-adiabatic terms. For the electron reservoir, the contribution of the adiabatic dephasing rate is shown to be significant compared to that of the non-adiabatic rate, in contrast to the case of a radiation reservoir. Other possible dephasing mechanisms, such as interaction with monochromatic radiation and the existence of multiple atomic levels, are studied as well.