Inelastic Collisions between Excited Alkali Atoms and Molecules. II. The Quenching of Sodium Resonance Radiation byN2,H2, HD, andD2

Abstract

The cross sections for quenching collisions between excited sodium atoms and ${\mathrm{N}}_{2}$, ${\mathrm{H}}_{2}$, HD, and ${\mathrm{D}}_{2}$ molecules in their electronic ground states have been determined using a delayed-coincidence method. The sodium atoms in mixtures with the gases were excited with 20-nsec pulses of NaD radiation, and the delays between the exciting and fluorescent pulses were measured with a time-to-pulse-height converter. The resulting pulse-height spectra, which were accummulated in a 400-channel kicksorter, yielded the effective lifetimes ${\ensuremath{\tau}}^{\ensuremath{'}}$ of the sodium resonance state, which are shorter than the natural lifetime $\ensuremath{\tau}$ because of the nonradiative decay induced in collisions with the molecules. The cross sections for collisions with ${\mathrm{N}}_{2}$, ${\mathrm{H}}_{2}$, HD, and ${\mathrm{D}}_{2}$, obtained from an analysis of the dependence of ${\ensuremath{\tau}}^{\ensuremath{'}}$ on the gas pressures, are 30.4\ifmmode\pm\else\textpm\fi{}1.2, 16.2\ifmmode\pm\else\textpm\fi{}0.3, 11.6\ifmmode\pm\else\textpm\fi{}0.4, and 9.8\ifmmode\pm\else\textpm\fi{}0.3 ${\mathrm{\AA{}}}^{2}$, respectively.