Collisional and thermal ionization of sodium Rydberg atoms I. Experiment for nS and nD atoms with n=8-20

摘要

Collisional and thermal ionization of sodium nS and nD Rydberg atoms withn=8-20 has been studied. The experiments were performed using a two-step pulsedlaser excitation in an effusive atomic beam at atom density of about 2 10^{10}cm^{-3}. Molecular and atomic ions from associative, Penning, and thermalionization processes were detected. It has been found that the atomic ions werecreated mainly due to photoionization of Rydberg atoms by photons of blackbodyradiation at the ambient temperature of 300K. Blackbody ionization rates andeffective lifetimes of Rydberg states of interest were determined. Themolecular ions were found to be from associative ionization in Na(nL)+Na(3S)collisions. Rate constants of associative ionization have been measured usingan original method based on relative measurements of Na_{2}^{+} and Na^{+} ionsignals.