Rotationally resolved photoelectron spectroscopic study of the Ã+ state of H2O+

This talk will present the analysis of the rotationally resolved pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectrum of H$_2$O and will be focussed on the $\tilde{A}^+$$\leftarrow$$\tilde{X}$ transitions. H$_2$O$^+$ in the $\tilde{A}^+$ state is predicted to be linear \footnote{M. Brommer, B. Weis, B. Follmeg, P. Rosmus, S. Carter, N. C. Handy, H. J. Werner, and P. J. Knowles, J. Chem. Phys. 98, 5222 (1993)}. The sensitivity and the high resolution of PFI- ZEKE photoelectron spectroscopy allowed us to observe the rotational structure of low bending vibrational levels of the $\tilde{A}^+$ state of H$_2$O$^+$ from the $\tilde{X}$ ground electronic state of H$_2$O. The assignment of the rotational structure of ionic levels previously observed by optical spectroscopy of the $\tilde{A}^+$ - $\tilde{X}^+$ band system of H$_2$O$^+$ \footnote{T .Huet, I. H. Bachir, J. L. Destombes, and M. Vervloet, J. Chem. Phys. 107,5645 (1997).} \footnote{H. Lew, Can. J. Phys. 54, 2028 (1976).} will be presented and the intensity distribution of the photoelectron spectrum will be discussed in terms of the even or odd nature of the orbital angular momentum quantum number $l$ of the photoelectron. Tentative assignments will be presented for several low-lying vibrational levels of the $\tilde{A}^+$ state and compared with theoretical predictions $^c$. They will also be discussed in terms of the rotational structure of higher $\tilde{A}^+$ vibrational levels of the same symmetry