Internuclear distance and effects of Born-Oppenheimer breakdown for PtS, determined from its pure rotational spectrum

Platinum monosulfide PtS has been prepared in its X0(+) ground electronic state by laser ablation of Pt in the presence of H(2)S. The rotational spectra of eight isotopic species have been measured with a cavity pulsed jet Fourier-transform microwave spectrometer. Spectral analysis using a multi-isotopomer Dunham-type expression produced values for Y(01), Y(02), Y(11), and Y(21), along with large values for Born-Oppenheimer breakdown (BOB) parameters for both atoms of the molecule. The BOB parameters are rationalized in terms of the molecular electronic structure and nuclear field shift effects. A large negative (195)Pt nuclear spin-rotation constant has been rationalized in terms of the electron-nucleus dipole-dipole hyperfine constant. The equilibrium bond length in the Born-Oppenheimer approximation has been evaluated.