Non-Adiabatic Atomic Transitions: Computational Cross Section Calculations of Alkali Metal-Noble Gas Collisions
Date of Award
Doctor of Philosophy (PhD)
Department of Engineering Physics
David E. Weeks, PhD.
Diode Pumped Alkali Lasers operate by exciting a gaseous cell of alkali metal to its P3/2 excited energy state. A noble gas, present in the cell, collisionally de-excites the alkali metal to its P1/2 state. The alkali atoms then relax to their S1/2 ground state by emitting photons. The non-radiative de-excitation due to inert gas atoms represents an interesting juncture for DPALs operation. This process must be faster than the radiative relaxation back to the S1/2 state for lasing to occur. The rate of non-radiative de-excitation is related to the collisional cross section and the cross section is related to the S-Matrix. A time-dependent algorithm, the Channel Packet Method, was implemented to predict S-Matrix elements for alkali metal - noble gas (MNg) collisions. The S-Matrix contains the close-coupled Hamiltonian of the MNg system in body-fixed coordinates represented in the P-Manifold of states. There were two major state-to-state coupling phenomena responsible for intramultiplet mixing: spin-orbit and Coriolis. A total of nine collisions were computationally simulated between Potassium, Rubidium, and Cesium and the noble gases Helium, Neon, and Argon. Temperature averaged cross-sections were calculated for the P1/2 to P3/2 transition and compared to experiment.
DTIC Accession Number
Lewis, Charlton D. II, "Non-Adiabatic Atomic Transitions: Computational Cross Section Calculations of Alkali Metal-Noble Gas Collisions" (2011). Theses and Dissertations. 1461.