INFRARED SPECTRUM OF THE $\nu_{1}$ FUNDAMENTAL BAND OF $H_{3}O^{+}$

Abstract

Infrared spectrum of $H_{3}O^{+}$ has been observed by a difference frequency laser spectrometer with positive column discharges of $H_{2}/O_{2}$ gas mixtures, which gave a spectrum remarkably simpler than the previous one with $H_{2}/O_{2}$/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 $H_{3}O^{+}$ were identified with the band origins of $3389.66 cm^{-1}$ and $3491.17 cm^{-1}$, 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.