MAGNETIC FIELD MODULATED INFRARED LASER SPECTROSCOPY OF THE $ClH_{2}{^{+}} V_{2}$ BAND
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Date
1986
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Ohio State University
Abstract
The chloronium ion ($ClH_{2}{^{+}})$ has been detected for the first time in the gas phase by infrared diode laser spectroscopy with magnetic field modulation. The absorption cell used was 1 m long, 6.5 cm i.d., and of white type multiple reflection type. A hollow cathode of 50 cm length was installed inside a solenoid magnet. A 3.8 kHz AC field of 76G peak-to-peak superimposed on a 37G DC field was employed to modulate the generation of ionic species. The $ClH_{2}{^{+}}$ ion was produced by a discharge of an $H_{2}$ (1 Torr), He (300 mTorr) and HCl (30 mTorr) mixture. One hundred and forty-eight lines were observed between $1040 cm^{-1}$ and $1330 cm^{-1}$, and 120 lines were assigned to the $\nu_{2}$ fundamental band of $^{35}ClH_{2}{^{+}}$ and 28 lines to that of $^{37}ClH_{2}{^{+}}$. The observed transitions have been analyzed by Watson's A-reduced Hamiltonian to determine band origins $(\nu_{2}(^{35}Cl) = 1184.126 cm^{-1}, v_{2} (^{37}Cl) = 1183.217 cm^{-1})$, rotational and centrifugal distortion constants. The $r_{0}$ structure of $^{35}ClH_{2}{^{+}}$ was determined as: $r_HCl = 1.3135(87)$ \AA and HClH $ = 94.3(1 2)^{\circ}$, which are in good agreement with ab inito calculation (1.306 A, 94.9$^{\circ}$) by $Botschwina.^{1}$
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$^{1}$ P. Botschwina, in Molecular Ions: Geometrical and Electronic Structures, edited by J. Berkowitz and K. Groeneveld (Plenum, New York, 1983). Address: Institute for Molecular Science, Okazaki 444, Japan.
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