Knowledge Bank

Infrared spectrum of $H3O+$ has been observed by a difference frequency laser spectrometer with positive column discharges of $H2/O2$ gas mixtures, which gave a spectrum remarkably simpler than the previous one with $H2/O2$/He $discharges.a$ After extending the previous assignment of the $\nu 3$ fundamental bands to higher J, K transitions, vibration-rotation structures due to the $\nu 1+\leftarrow 0-$ and $\nu 1-$ bands of $H3O+$ were identified with the band origins of $3389.66cm-1$ and $3491.17cm-1$, respectively, in the region of the strong $\nu 3\pm \leftarrow 0\pm$ bands. Molecular constants for the $\nu 1\pm \leftarrow 0\pm$ bands were obtained by the least-squares fittings for the observed frequencies. Coriolis interactions between the $\nu 1$ and $\nu 3$ vibrations have been considered to explain some large deviations of the observed transitions from the calculated frequencies in the $\nu 1$ and $\nu 3$ bands.