The rotational spectra, potential function, Born-Oppenheimer breakdown, and magnetic shielding of SnSe and SnTe

The pure rotational spectra of 27 isotopic species of SnSe and SnTe have been measured in the frequency range of 5-24 GHz using a Fabry-Perot-type resonator pulsed-jet Fourier-transform microwave spectrometer. Gaseous samples of both chalcogenides were prepared by laser ablation of suitable target rods and were stabilized in supersonic jets of Ar. Global multi-isotopolog analyses of all available high-resolution data produced spectroscopic Dunham parameters Y-01, Y-11, Y-21, Y-31, Y-02, and Y-12 for both species, as well as Born-Oppenheimer breakdown (BOB) coefficients delta(01) for Sn, Se, and Te. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X (1)Sigma(+) electronic state of both SnSe and SnTe. Additionally, the magnetic hyperfine interaction produced by the dipolar nuclei Sn-119, Sn-117, Se-77, and Te-125 was observed, yielding first determinations of the corresponding spin-rotation coupling constants.