Submillimeter-Wave Spectra of H2Cl+ and its Isotopic Species: Molecular Structure

Abstract

The rotational spectra of HD35Cl+, H235Cl+, and H237Cl+ were measured in the frequency region of 180 to 550 GHz with a source-modulated submillimeter-wave spectrometer. The ions were generated in a free space absorption cell by a hollow-cathode discharge in a gas mixture of Cl2 and He to which H2 and/or D2 was added. Precise molecular constants including the electric quadrupole coupling constants were determined for the three species. The zero-point average structure, rz, was calculated from moments of inertia corrected for harmonic terms. The harmonic force field of H2Cl+ was derived from previously estimated harmonic vibrational frequencies and inertial defects. The rz structures obtained are rz(Cl–H)=1.320 57(48)Å and θz(H–Cl–H)=94.238(72)° for H235Cl+ and rzCl–H)=1.320 60(38)Å and θz(H–Cl–H)=94.239(58)° for H237Cl+, where values in parentheses indicate errors due to residual inertial defects among the corrected moments of inertia. When the θz of HD35Cl+ is assumed to be the same as that of H235Cl+, the rz(Cl–H) and rz(Cl–D) lengths of HD35Cl+ are calculated to be 1.320 69(69) Å and 1.316 54(111) Å, respectively.