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

Abstract

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⁺.

Keywords:

• PFI-ZEKE photoelectron spectroscopy
• water
• MATI

Acknowledgements

We thank Dr Bérenger Gans, Orsay, and Dr Thérèse Huet, Lille, for useful discussions. This work was supported financially by the Swiss National Science Foundation under project Nr. 200020-146759.