Potential Energy Curve of the Excited State of KH

The ${}_{}{}^1{}_{}{}^{}\Sigma \to {}_{}{}^1{}_{}{}^{}\Sigma$ spectrum of KH has been photographed at large dispersion and the region from 4150A to 4650A has been analyzed. Previous analyses of the spectrum have on the whole been verified, although certain discrepancies in molecular constants have been removed. For the purpose of testing Mulliken's explanation of the anomalous character of the excited state of an alkali hydride, a potential curve has been constructed for the excited state of KH, by the use of Klein's method. The vibrational energy of the upper state of KH has been followed to about three-fourths of the energy of dissociation, farther than in any other alkali hydride. As in LiH, the curve of the excited state crosses the ionic curve (of ${\mathrm{K}}^{+}$ and ${\mathrm{H}}^{-}$) and dissociates apparently into $\mathrm{K}\left({}_{}{}^2{}_{}{}^{}P\right)$ and $\mathrm{H}\left({}_{}{}^2{}_{}{}^{}S\right)$. The relative position of the molecular and ionic curves is in reasonable agreement with Mulliken's hypothesis.