Observation of Fluorescence of the HeH Molecule

Abstract

This Letter reports the first spectroscopic detection of HeH, the simplest excimer molecule that can exist. He${\mathrm{H}}^{*}$ is produced in electronically excited states in reactions between He and ${\mathrm{H}}_{2}$ excited selectively by synchrotron radiation into the $C^{1}\ensuremath{\Pi}_{\mathrm{u}}({v}^{\ensuremath{'}}>~1)$ or $B^{1}\ensuremath{\Sigma}_{\mathrm{u}}^{+}({v}^{\ensuremath{'}}>~11)$ state. He${\mathrm{H}}^{*}$ emits a broad characteristic fluorescence continuum between 200 and 400 nm which is attributed to $B^{2}\ensuremath{\Pi}\ensuremath{\rightarrow}X^{2}\ensuremath{\Sigma}^{+}$.