Infrared laser spectroscopy of the 21 and 221 bands of H2O+(<i>X</i> 2<i>B</i>1)

Infrared laser absorption spectra of H2O+ have been recorded in an ac discharge using velocity modulation detection. Eighty-five lines of the 210 fundamental and 20 lines of the 221 hot band were used to derive rotation, spin-rotation, and distortion parameters for the ground state and the first two vibrationally excited states of the bending mode. The results are compared with those from analysis of the ÖX̃ band system and from rotational and vibration–rotation laser spectra, as well as with recent ab initio results obtained using MRCI wave functions.