Bound excited states of HeH: Predissociation ofAΣ+2and radiative dissociation fromBΠ2

Abstract

Bound excited states of HeH, formed by electron capture in a beam of 6-keV He${\mathrm{H}}^{+}$ ions passing through Cs vapor, were observed to undergo both predissociation and radiative dissociation. Measurement of the kinetic energy spectrum of the H-atom products was facilitated by their conversion to ${\mathrm{H}}^{-}$. Transformation of the laboratory energy spectrum to the 0° and 180° center-of-mass energy release spectra reveals a broad peak at about 8.4 eV, consistent with predissociation from several vibrational levels of the qq$A{}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ state, and a lower peak at about 3.3 eV, resulting from the $B{}_{}{}^2{}_{}{}^{}\Pi \to X{}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ radiative decay recently observed by Möller, Beland, and Zimmerer.