OBSERVATION OF HOT BANDS OF $H^{+}_{3}$ USING AN EXTENDED DIFFERENCE FREQUENCY SPECTROMETER

$^{1}$ S. Yu.Volkov et al., SoV. J. Quantum Electron., 11, 135 (1981). $^{2}$ S.Miller and J. Tennison, J. Mol. Spet., 126, 183 (1987) and private comununication AT\&T PhD. ScholarAuthor Institution: Herzberg Institute of Astrophysics, National Research councilWe have extended the range of our difference frequency spectrometer from the previous range of $4200-2300 cm^{-1}$ to $5400. 1850 cm^{-1}$ by using an angle-tuned $LilO_{3}{^{1}}$ rather than the temperature-tuned $LiNbO_{3}$ as the non-linear optical mixing element. Although the infrared conversion efficiency is much lower for $LilO_{3}$ than for $LiNbO_{3}$ we have found this extended coverage to be useful in our search for the hot bands of $H_{3}^{+}$. We have observed many transitions of $H_{3}^{+}$ not assignable to the $\nu_{2} \leftarrow O$ fundamental band using a liquid nitrogen cooled AC discharge with 600 in torr $H_{2}$ and 7 Torr He. Many of the lines have been assigned to the $2\nu_{2} \ell=2\leftarrow \nu_{2}, \ell=1$. band based on the recent calculation of Miller and $Tennison^{2}$. We expect most of the remaining lines to belong to the $2\nu_{2} \ell=0 - \nu_{2} , \ell=1$ and $\nu_{1} + \nu_{2}$ hot bands