Threshold photoelectron spectroscopy of H2O and D2O over the photon energy range 12-40Â eV

The threshold photoelectron spectra of H2O and D2O have been recorded over the ionization region (12-40 eV) under high-resolution conditions using synchrotron radiation. Extensive vibrational 'filling-in' is found in the Franck-Condon gap regions between the three lowest ionic-state band systems that is attributed to autoionization of Rydberg states lying in these binding-energy regions. Vibronic coupling effects are found in the A 2A1 band system of H2O+ and D2O+ in general agreement with a previous experiment. An unusual intensity enhancement is found in the B 2B2 band system in the threshold photoelectron spectra of H2O and D2O that is attributed to an enhanced production of H2O+ and D2O+ ions due to the autoionization of Rydberg states lying in the binding energy region of this electronic state. In the inner valence ionization region two broad features have been found that are attributed to the (2a1)−1 'main-line' state and the (1b1)14a1∗ resonant state.