Threshold ionization spectroscopy of H2O, HDO and D2O and low-lying vibrational levels of HDO+and D2O+

Rotationally resolved photoelectron spectra of jet-cooled H2O, HDO and D2O have been recorded near the origin of the photoionising transition following single-photon ionization using the complementary techniques of mass-analysed threshold-ionization (MATI) and pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy. A gas mixture of H2O, HDO and D2O with Ar was obtained by mixing H2O (ℓ) and D2O (ℓ) in a reservoir and bubbling Ar gas through the mixture. To unambiguously assign the photoelectron bands to H2O, HDO or D2O, the PFI-ZEKE photoelectron spectra of the mixture were compared to MATI spectra and to spectra of H2O. Analysis of the rotational structure of the origin bands (v+1 = 0, v2+ = 0, v+3 = 0) ← (v1 = 0, v2 = 0, v3 = 0) of H2O, HDO and D2O and of the transitions to the (010), (020) and (100) levels of D2O+ and the first excited level of the O–D stretching mode of HDO+ provided new information on the photoionization dynamics of water and the energy level structure of HDO+ and D2O+