Collisional quenching and radiation trapping kinetics for Rb(5p) in the presence of ethane

摘要

Optically pumped alkali vapor lasers have been constructed using excitation of the D_2 line (~2P_(3/2)-~2S_(1/)2) followed by lasing on the D_1 line (~2P_(1/2)-~2S_(1/ 2)). Collisional relaxation is used to transfer population from ~2P_(3/2) to the ~2P_(1/2) level. The collision partner used for this step must have a large cross section for inducing transfer between the ~2P_J levels, combined with a very small cross section for electronic quenching of the form twr(a~n2sPf_eJr) +aQge→nMt).(~2S_(1/2))+Q (where M is an alkali metal and Q is the energy Ethane has proved to be an effective energy transfer agent for optically pumped Rb and Cs lasers. However, modeling of data for the Rb/C2H6 laser with the literature value for the quenching rate constant was unsuccessful. We have reexamined the quenching of Rb(~2P_J) by C_2H_6 using time-resolved fluorescence techniques. Radiation trapping was significant under the conditions of our measurements, and an analysis of the interplay between the kinetics of trapping and quenching was carried out. It was found that quenching of Rb(~2P_J) by C_2H_6 was very inefficient. The upper bound established for the quenching cross section was two orders of magnitude lower than that indicated by the previous determination.