Absolute Fluorescence Yields from Electron-Irradiated Gases. 2. KrF* and XeF*

Abstract

Absolute total fluorescence yields for the KrF*(B,C) and XeF*(B,C) states have been determined from pulse-electron-irradiated Kr/SF6 and Xe/SF6 gas mixtures. By application of established formation and quenching mechanisms and rate constants, the KrF* yield has been resolved into its two constituent components, corresponding to exciplex formation by excited-state reaction of Kr species and ionic recombination. The initial yield of electronically excited krypton atoms that can react with SF6, Kr* + SF6 → KrF* + products, was determined to be G o* = 0.70 ± 0.10, while the corresponding three-body ionic recombination reaction, Kr2 + + SF6 - + Kr → KrF* + products, gave G o + = 1.70 ± 0.10. Analogous studies of the XeF* emission showed that ionic recombination is essentially the only formation pathway, with a calculated initial fluorescence yield for the reaction Xe2 + + SF6 - + Xe → XeF* + products of G o + = 0.26 ± 0.02. The experimental values are compared to the predictions of current theoretical models, and the importance of alternative reaction pathways is discussed.