Sensitized Fluorescence in Vapors of Alkali Atoms XIV. Temperature Dependence of Cross Sections for 7²P_1/2–7²P_3/2 Mixing in Cesium, Induced in Collisions with Noble Gas Atoms

Abstract

The cross sections for 72P1/2–72P3/2 excitation transfer in cesium, induced in collisions with noble gas atoms, have been determined in a series of sensitized fluorescence experiments at temperatures ranging from 405 to 630 K. The cross sections which lie in the range 0.06–20 Å2, exhibit a temperature dependence which, however, is less pronounced than in the more adiabatic case of the cesium resonance doublet.

Temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer and for quenching in cesium, induced in collisions with H2, N2, CH4, and CD4

“…The various cross sections exhibit a variation with temperature, which is about as extensive as in the case of the cesium resonance doublet (2,13). Their values exceed by some two orders of magnitude the corresponding cross sections for collisions with noble gas atoms except for helium (3,14), and are comparable with cross sections reported by Rocchiccioli (15) for transfers from C S~~P~,~ to 8?P31?, 72D312, and 72D512 induced in collisions with N2 and H2, bearing in mind differences in the energy defect AE. The large sizes of the cross sections Q~~ suggest that the energy defect between the fine structure states is interconverted not only with the kinetic energy of relative motion as it is in the case of the collisions with noble gas atoms, but also with molecular rotational energy.…”

“…The final values of the collision numbers Z12, Z z I , Zlx, and Zx were obtained by an iteration procedure and were used in conjunction with [lo] to calculate the mixing and effective quenching cross sections. Figure 2 shows a plot of the collision numbers yielded by [3] against N? pressure and is representative of all the other mixtures.…”

“…Equat~ons [2] and [3] are strictly valid only if imprisonment of radiation is negligible. Radiation trapping has been avo~ded by working at a cesium vapor pressure lower than 4.5 x lo-' Torr, at which it was found to be absent.…”

“…The cross sections for the very much less adiabatic 7'PI,' o 7'P3,2 transfers were also found to vary somewhat with temperature (3). An analysis of the isotope effect which was discovered in the 6'Pl,z o 6'P3,2 cross sections for collisions with all the deuterated methanes, has led to the conclusion that the transfer of excitation proceeds by a mechanism which involves electronic-to-rotational energy transfer (4).…”

Spin-orbit relaxation and quenching of cesium 72Pin mixtures of helium, methane, and ethane

“…However, the fine-structure relaxation and collisional quenching of these states are relatively unstudied. For Cs 7 2 P 3/2,1/2 , there are several older reports of rapid fine-structure mixing by rare gases [9][10][11] and molecular collision partners [12], but not for the important laser species, ethane. The corresponding quenching rates, their dependence on spin-orbit split state, and the product states are largely unavailable.…”