Pressure Shifts and Quenching of Atomic and Molecular States Produced in Electron-Bombarded Liquid Helium

Abstract

The optical absorption and emission spectra of electron-bombarded liquid helium has been studied as a function of pressure between the saturated vapor pressure and 25 atm. The transitions of ${\mathrm{He}}^{*}$ and ${\mathrm{He}}_2^{*}$ in the liquid shift toward the blue with increasing pressure. The observed line profile and pressure shift of the $\mathrm{He}\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}P\right)\leftarrow \mathrm{He}\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}S\right)$ atomic absorption line are in good agreement with recent static line broadening calculations. We also report a strong pressure-dependent quenching of the excited atomic and molecular states in the liquid.