(2+1) Resonance-enhanced multiphoton ionization (REMPI) and (2+1 ') mass-analyzed threshold ionization (MATI) spectroscopy of H2O

Rotationally resolved MATI spectra of H2O, recorded using two-colour (2 + 1 ') multiphoton excitation via the C state, are reported. The spectroscopy p rovides a possible route to clean state-selection of rovibronic levels of t he H2O+ ion. The rotational line intensities observed in the spectra are di scussed in relation to previous photoelectron spectra and theoretical calcu lations. The observation of intense Delta K-a = even transitions is attribu ted to a large contribution to the transition moment from an nf <-- nd comp onent. Room temperature and jet-cooled (2 + 1) REMPI spectra of H2O are als o reported for the region 80000-92000 cm(-1). These involve two-photon tran sitions from the ground (X) over tilde (1)A(1) state to various vibrational levels of the (C) over tilde B-1(1), (D) over tilde' B-1(1) and (D) over t ilde " (1)A(2) states as well as the first linear B-1(2) state.