The absorption spectra of H2O+ and D2O+ in the visible and near infrared region

The absorption spectra of the electronic transition of H2O+ and D2O+ are investigated in the visible region from 16 400 to 17 600 cm−1 and in the near infrared region from 12 200 to 14 000 cm−1 using optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy (OH-MR-VMS). Three subbands including 111 spectral lines of H2O+ and seven subbands including 209 spectral lines of D2O+ are observed and analysed, among which four subbands, Σ (0,9,0)−(0,0,0), Δ (0,9,0)–(0,0,0), Π (0,8,0)–(0,0,0) and Π (0,10,0)–(0,0,0) of D2O+ in the near infrared region are studied for the first time. Holding the molecular constants of the lower state fixed at the published values, a set of molecular constants and rotational energy terms for each observed vibronic level of the upper state are obtained.