Vacuum-ultraviolet emission from high-pressure xenon and argon excited by high-current relativistic electron beams

Abstract

High pressure Xe and Ar were excited by high-current relativistic-electron bursts. The spectral and temporal characteristics of the uv continua, centered near 1700 \AA{} in Xe and 1260 \AA{} in Ar, were measured. The maximum of the Xe spectral distribution shifted from 1690 \ifmmode\pm\else\textpm\fi{} 9 to 1710 \ifmmode\pm\else\textpm\fi{} 9 \AA{}, and the spectral width decreased from 150 \ifmmode\pm\else\textpm\fi{} 3 to 110 \ifmmode\pm\else\textpm\fi{} 3 \AA{} when the pressure was raised from 2 to 34 atm. The shift of the Ar continuum centered at 1260 \ifmmode\pm\else\textpm\fi{} 9 \AA{} was negligible and the spectral width decreased from 130 \ifmmode\pm\else\textpm\fi{} 3 to 90 \ifmmode\pm\else\textpm\fi{} 3 \AA{} when the pressure was raised from 2 to 61 atm. Exponential time constants for the buildup and decay of the Xe and Ar continua were obtained. They are characterized by a ${p}^{\ensuremath{-}1.5}$ pressure dependence below 3 atm. Pressure-independent decay time constants of 4 \ifmmode\pm\else\textpm\fi{} 1, 16 \ifmmode\pm\else\textpm\fi{} 2.5, and about 280 nsec were obtained for Xe at high pressure. For Ar the pressure-independent decay time constants were 6 \ifmmode\pm\else\textpm\fi{} 1.5, 30 \ifmmode\pm\else\textpm\fi{} 5, and about 230 nsec. The efficiency for conversion of electron kinetic energy to uv energy was 10 \ifmmode\pm\else\textpm\fi{} 4% in Xe and 15 \ifmmode\pm\else\textpm\fi{} 7% in Ar.