INFRARED STUDIES OF THE $v_{4}$ BAND OF $CH_{2}D^{+}$

During our studies of the infrared spectra of $HCCD^{+}$ $^{1}$ we have also scanned parts of the $v_{4}$ fundamental vibrational rotational band of $CH_{2}D^{+}$. The monodeuterated methyl cation is produced in a liquid nitrogen-cooled AC-glow discharge with a gas mixture of He:$H_{2}$ : $CD_{4}$: $CH_{4}$ (700:4:4:1 or 7000:10:12:1) with a total pressure of = 7 torr. The spectra of the species were recorded using a difference frequency spectrometer and velocity modulation. The detailed analysis of the v4 vibrational rotational band is underway. The monodeuterated methyl cation is of special interest for radioastronomical search of the acetylene ion in interstellar space and planetary ionospheres because of the presence of an effective permanent dipole moment. The methyl cation is a very important intermediate in the formation of intersellar molecules. $^{1}$M.-F. Jagod, M. R\\"{o}sslein, C. Gabrys, B. D. Rehfuss, F. Scappini, M. W. Crofton and T. Oka, J. Chem. Phys. to be sub. (1991)