Collisional and radiative excitation transfers in Kr-Xe mixtures: Quenching of Kr.

Abstract

A detailed study of electronic energy transfers in Kr-Xe mixtures has been made using a 250-keV electron accelerator to excite Kr-Xe mixtures over a wide range of Kr-host-gas pressure and Xe-impurity concentrations. Kr pressure ranged from 25 to 900 Torr with Xe concentrations varying from 0.1% to 10% of Kr partial pressure. Emission spectra taken in the vacuum-ultraviolet (vuv) region indicate that energy is transferred efficiently from Kr to Xe, with radiation from the Xe${(}^{3}$${P}_{1}$) state becoming greatly enhanced as the Xe-impurity concentration is increased. Emission spectra from the vuv also show that the Xe${(}^{1}$${P}_{1}$) state is populated by absorption of photons emitted from the ${\mathrm{Kr}}_{2}$${\mathrm{}}^{\mathrm{*}}$ first continuum. Two-body quenching rates with Xe ground-state atoms have been found for the Kr${(}^{1}$${P}_{1}$) [${k}_{q}$(1165 \AA{})=1.2\ifmmode\times\else\texttimes\fi{}${10}^{5}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$/Torr] and for the Kr${(}^{3}$${P}_{1}$) [${k}_{q}$(1236 \AA{})=9.5\ifmmode\times\else\texttimes\fi{}${10}^{5}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$/Torr] resonance states. Time-resolved measurements have also been made on the ${\mathrm{Kr}}_{2}$${\mathrm{}}^{\mathrm{*}}$ first and second continua. These measurements show the Kr${(}^{3}$${P}_{1}$) state is the atomic precursor of the ${\mathrm{Kr}}_{2}$${\mathrm{}}^{\mathrm{*}}$ first continuum. The results obtained in the ${\mathrm{Kr}}_{2}$${\mathrm{}}^{\mathrm{*}}$ second continuum are rate limited by the decay of Kr${(}^{3}$${P}_{1}$) at large Xe-impurity concentrations.