Ultraviolet Spectra of BeH and BeH+

Abstract

A BeH band system analogous to the $B^{2}\ensuremath{\Pi}\ensuremath{\rightarrow}X^{2}\ensuremath{\Sigma}$ MgH system is reported. Observed bands are the (0,0) at 1960A, (1,0) at 1882A and (1,1) at 1956A. Each consists of a single $Q$ branch (negligible spin doubling), $P$ and $R$ branch transitions being eliminated by predissociation from the $^{2}\ensuremath{\Pi}$ state into a neighboring unstable $^{2}\ensuremath{\Sigma}$ state. For the $^{2}\ensuremath{\Pi}$ state ${B}_{0}=10.65$ ${\mathrm{cm}}^{\ensuremath{-}1}$ and ${\ensuremath{\omega}}_{e}\ensuremath{-}2{x}_{e}{\ensuremath{\omega}}_{e}=2133.4$. The complex BeH spectrum from 3100A to 3600A consists only of an extension of the known $^{1}\ensuremath{\Sigma}^{+}\mathrm{rightarrow}^{1}\ensuremath{\Sigma}^{+}$ Be${\mathrm{H}}^{+}$ system. Analyses of the principal Be${\mathrm{H}}^{+}$ bands in this region yield revised values for the band constants.