# INFRARED STUDIES OF THE $\nu_{3}$ BAND OF $CH_{2}^{+}$

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 Title: INFRARED STUDIES OF THE $\nu_{3}$ BAND OF $CH_{2}^{+}$ Creators: Gabrys, C. M.; Uy, Dairene; Jagod, M.- F.; Oka, T. Issue Date: 1994 Publisher: Ohio State University Abstract: The spectrum of the $CH_{2}^{-}$ ion is difficult to analyze because of the existence of the Renner-Teller effect and a low barrier to linearity. In our previous $study^{1}$ of the $\nu_{3}$ band of $CH_{2}^{+}$, we could assign only 18 lines in the $K_{a}=0$ series of the $\alpha$-type parallel transition because of the irregularity of other series and because of the complexity of the overall spectrum due to other carbocations in the plasma. In order to maximize $CH_{2}^{-}$ signals as opposed to those of $CH_{3}^{+}$, we chose a plasma similar to the one in our initial scan but without $H_{2}$ since. $CH_{4} + He^{*} \stackrel{70%}{\rightarrow} CH_{2}^{+} \stackrel{H_{3}}{\rightarrow} CH_{3}^{-}.$ We found that a mixture of $CH_{4}$/He=90mT/7 Torr in a liquid-$N_{2}$ cooled positive column clearly distinguishes the object of our quest. An extensive scan around the band origin of $\nu_{3}=3131 cm^{-1}$ using such conditions allowed us to unambiguously assign the tow series for $K_{a}=1$ and some lines with $K_{a}=2$. The series are quite irregular because of the Renner-Teller perturbation in the $\nu_{3}$ state, but the ground state combination differences are fairly regular. Altogether, 45 transitions the been assigned, and 15 combination differences in the ground state have been fitted. Description: $^{1}$M. R\""{o}sslein, C. M. Gabrys, M.-F. Jagod, and T. Oka, J. Mol. Spectrosc. 153, 738-740 (1992) Author Institution: Department of Chemistry, University of Chicago URI: http://hdl.handle.net/1811/13268 Other Identifiers: 1994-TE'-06