Microwave spectrum, geometry, and hyperfine constants of PdCO

The pure rotational spectrum of palladium monocarbonyl, PdCO, has been measured between 6000 and 24 000 MHz using a cavity pulsed jet Fourier transform microwave spectrometer. The molecules were prepared by laser ablation of Pd in the presence of CO contained in an Ar backing gas. The spectra of 15 isotopomers have been used to determine the molecular geometry from the measured rotational constants. Centrifugal distortion constants are in good agreement with those calculated from a literature harmonic force field. A nuclear quadrupole coupling constant and nuclear spin-rotation constant have been determined for ¹⁰⁵Pd. Nuclear shielding parameters have been evaluated from the measured spin-rotation constant. The geometry is discussed with reference to theoretical data and to other molecules containing an M-CO bond.