Knowledge Bank

The chloronium ion ($ClH2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>})$ 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 $ClH2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ ion was produced by a discharge of an $H2$ (1 Torr), He (300 mTorr) and HCl (30 mTorr) mixture. One hundred and forty-eight lines were observed between $1040cm-1$ and $1330cm-1$, and 120 lines were assigned to the $\nu 2$ fundamental band of $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}ClH2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ and 28 lines to that of $\mathrm{<mrow\; data-mjx-texclass="ORD">37</mrow>}ClH2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$. The observed transitions have been analyzed by Watson's A-reduced Hamiltonian to determine band origins $(\nu 2(35Cl)=1184.126cm-1,v2(37Cl)=1183.217cm-1)$, rotational and centrifugal distortion constants. The $r0$ structure of $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}ClH2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ was determined as: $rHCl=1.3135(87)$ \AA and HClH $ = 94.3(1 2)^{\circ}$,whichareingoodagreementwithabinitocalculation(1.306A,94.9$^{\circ}$) by $Botschwina.1$