High-resolution photoelectron-spectroscopic investigation of the H$_2$O$^+$ cation in its ${\mathrm {\tilde A^+}}$ electronic state

Abstract: The photoelectron spectrum of water has been recorded in the vicinity of the ${\mathrm {\tilde A<sup>+}}$ $\leftarrow$ $\tilde{\mathrm{X}}$ transition between 112 000 and 116 000 cm$<sup>{-1}$ (13.89-14.38 eV). The high-resolution allowed the observation of the rotational structure of several bands. Rotational assignments of the transitions involving the $\Pi(080)$, $\Sigma(070)$ and $\Pi(060)$ vibronic states of the $\tilde{\mathrm{A}}<sup>+$ electronic state are deduced from previous studies of the $$\tilde{\mathrm{A}}⁺ - \tilde{\mathrm{X}}<sup>+$$ band system of H$_2$O$<sup>+$ (Lew, Can. J. Phys. 54, 2028 (1976) and Huet et al., J. Chem. Phys. 107, 5645 (1997)) and photoionization selection rules. The transition to the $\Sigma(030)$ vibronic state is tentatively assigned.