Photolytic spectroscopy of simple molecules. III. The selective photolysis of CsKr and Cs2Kr at visible wavelengths

Abstract

In this work a two-photon technique was used for the measurement of the relative cross sections for the selective photolysis of an equilibrium distribution of CsKr and Cs2Kr populations existing at 523 °K in the presence of 0.132 amagat Kr. The cross sections for photolysis that selectively produced the lowest four excited states of Cs were obtained. Over the wavelength range 420 to 660 nm, the resulting dispersion curves showed one major feature which could be attributed to CsKr, the 6sσ→ 5dσ band dissociating to produce Cs(5 2D5/2). Various considerations indicated that the other structures observed in the spectrum belonged to the trimer Cs2Kr formed from Cs2 through the attraction of a Kr by polarization forces. The occurrence in the spectra of both CsKr and Cs2Kr of relatively broad photolysis bands leading to extremely selective distributions of product state populations was found to be fairly common. As in the previous work with Cs2 it was observed that adiabatic and, hence, state-selective dissociation occurred if the photolysis was excited at a transition energy not too much in excess of the threshold for the process. An examination of the kinetics of the photolysis products gave rate coefficients for the mixing and quenching of the fine structure components of Cs (5 2D) of 7×10−12 and 3.7×10−13 cm3 sec−1, respectively. At the densities used in this experiment these implied that useful populations of single states of Cs could be photolytically pumped with broadband radiation for periods of the order of tens of nanoseconds, while populations of energy levels could be pumped for more than an order of magnitude longer period of time.