Rotational spectroscopy of jet-cooled molecular ions and ion complexes

Rotational spectra of the molecular ions HOCO+ and HOCS+, and the ion complexes, D3+Ar and sym-D2H+Ar were observed in a supersonic-jet expansion by using a Fabry-Perot type Fourier-transform microwave spectrometer cooperated with a pulsed discharge nozzle. Ion-formation efficiency for HOCS+ relative to the parent molecule under applied conditions was estimated to be ≈ 10−4. Tunneling splitting in the lowest rotational transition of D3+-Ar was not resolved within the experimental linewidth of ≈ 100 kHz.