Rotational spectrum of the Kr–HCO+ ionic complex

The Kr–HCO+ ionic complex and its isotopomers have been detected for the first time by Fourier transform microwave spectroscopy, where pure rotational transitions have been observed for six isotopomers under a jet-cooled condition. The rotational and the centrifugal distortion constants of the six isotopomers have been determined by least squares fittings. The complex has been determined to have a linear proton-bound form, with a Kr–H distance to be 2.222 Å and an estimated intermolecular stretching frequency of 129 cm−1. Results of Kr–HCO+ are compared with those of Ar–HCO+ and neutral complexes containing Kr.