Bending vibration of platinum monocarbonyl PtCO: observation of the millimeter- and submillimeter-wave spectra in the ν2 excited vibrational state

The millimeter- and submillimeter-wave spectra of PtCO in the ground and ν2 excited vibrational states were observed by employing a source-modulated microwave spectrometer. The PtCO molecule was generated in a free space cell by the sputtering reaction from a platinum sheet lining the inner surface of a stainless steel cathode using a dc glow plasma of CO and Ar. From the molecular constants determined for the ν2 excited state, especially the l-type doubling constant, its harmonic wavenumber was determined to be ≈420 cm−1, which resolved the reported discrepancy between the previous matrix-infrared and theoretical estimates.