Biography
Biography: Cristian Bahrim
Abstract
Depolarization of atoms is an angular momentum relaxation process which includes misalignment, disorientation and destruction of alignment. Th e alignment relaxation processes are for an axially symmetric ensemble of atoms excited evenly on Zeeman states |JM>; while disorientation is for the case of an asymmetric ensemble of atoms. Depolarization processes offer accurate information about the anisotropic interaction between atoms in the collision. Our quantum mechanical model for Neon*-Helium collisions offers theoretical depolarization rates for a wide temperature range. In particular reports, our KDA misaligment rate coefficients for Ne*(2pi [J=1]) atoms induced by collisions with Helium ground state atoms and comparison with experiments done in atomic discharges at temperatures between 10 K and 3000 K is reported. Our full quantum closecoupling many-channel calculations use a model potential for describing the interaction between Ne*(2pi [J=1]) and Helium ground state atoms and include the Coriolis coupling due to the rotation of the internuclear axis. Th e analysis of isotropic collisions in a gaseous mixture at thermal equilibrium indicates that for temperatures above 77 K the anisotropy factor between the collisional channels determines the dependence of the depolarization rates. For temperatures below 77 K, our rates for the Ne*(2p2 [J=1]) and Ne*(2p10 [J=1]) atoms indicate a greater infl uence from the long-range Coulomb potentials. We can conclude that when the depolarization depends weakly on the long-range Coulomb polarization and van der Waals potentials, the cross sections for our intra- and inter-multiplet transitions tend to have a linear variation toward the zero collision energy limit. Our quantum calculations indicate that for the Ne*(2p2) and Ne*(2p10) atoms at low collision energies, below 10 meV, the rotation of the atomic nuclei has a greater infl uence in the Hamiltonian of the Neon* - Helium system than the electrostatic interaction. Th is does not happen for the other atomic states, such as the 2p5 and 2p7 states, where the long-range part of the anisotropy in the electrostatic interaction has a much larger value. Our study helps to better understand the infl uence of collisions to the stability of atomic susceptibilities for quantum systems coupled with two or more lasers which are set up in an electromagnetically induced transparency regime and suggests the importance of inter- and intra-multiplet transitions to the thermal stability of quantum optical memories.