WF05		15min2:38

YASUHIRO OHSHIMA, Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-01, JAPAN; YOSHIHIRO SUMIYOSHI AND YASUKI ENDO, Department of Pure and Applied Sciences, Faculty of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo 153, JAPAN.

Microwave spectra of complexes bearing molecular ions, Ar-D₃⁺/HD₂⁺ and Ar-HCO⁺, were explored in a jet-cooled condition. The ionic complexes were formed by a pulsed electric discharge in a supersonic expansion. Their transitions were observed in the centimeter-wave region (7-40 GHz) with a Fourier-transform microwave spectrometer, guided by the previous millimeter-wave study in a static cell or the recent infrared photodissociation study in a mass-selected ion beam.

For Ar-HCO⁺, rotational transitions of mono-substituted species on H, C, and O were also measured. The isotopic substitution has confirmed the linear Ar···H-C-O configuration with the Ar···H distance of 2.13 Å. The centrifugal-distortion constant for Ar-HCO⁺ is two order of magnitude smaller than that for Ar-HCN, indicating much stronger binding in the ionic complex than the isoelectronic neutral counterpart.