The Band Spectrum of OH+

Two bands at 3332 and 3565A discovered by Rodebush and Wahl in the electrodeless discharge in pure water vapor, and two new bands at 3695 and 3893A, are shown to be, respectively, the (1,0), (0,0), (1,1) and (0,1) bands of O${\mathrm{H}}^{+}$. Rotational analysis establishes that they correspond to a ${}_{}{}^3{}_{}{}^{}\Pi \to {}_{}{}^3{}_{}{}^{}\Sigma _{}^{-}{}_{}{}^{}$ transition in which the ${}_{}{}^3{}_{}{}^{}\Pi$ state is inverted, with coupling intermediate between cases $a$ and $b$. The nine strong branches to be expected in this type of transition are found, and also enough satellite branches (nine in the 0,0 band) to determine the multiplet intervals in both states. The $\Lambda$ type doubling is large and there are exceptionally large perturbations in the $3b$, $2a$ and $1b$ levels of the $v^{\prime }=1\mathrm{}$ state, with maxima at approximately $K^{\prime }=18.5,14.5\mathrm{} \mathrm{and} 10.5$, respectively. These perturbations are attributed to another ${}_{}{}^3{}_{}{}^{}\Sigma _{}^{-}{}_{}{}^{}$ state. The ${}_{}{}^3{}_{}{}^{}\Sigma _{}^{-}{}_{}{}^{}$ state concerned in the transition and the perturbing state are molecular levels which dissociate into the ground states of O and ${\mathrm{H}}^{+}$ and ${\mathrm{O}}^{+}$ and H, respectively, but one cannot tell which is which. The ${}_{}{}^3{}_{}{}^{}\Pi$ state probably dissociates into the ground states of O and ${\mathrm{H}}^{+}$.