Rotational spectra, potential function, Born-Oppenheimer breakdown and magnetic shielding of SiSe and SiTe

The pure rotational spectra of 18 isotopic species of SiSe (8) and SiTe (10) have been measured in their X1Σ+ electronic state with a pulsed-jet resonator Fourier transform microwave spectrometer. The molecules were prepared by a combined DC discharge/laser ablation technique and stabilised in a supersonic jet of Ar. Global multi-isotopologue analyses yielded spectroscopic Dunham parameters Y01, Y11, Y21, Y31 and Y02 for both species, as well as effective Born-Oppenheimer breakdown (BOB) coefficients δ01 for Si, 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 X1Σ+ electronic state of both SiSe and SiTe. Additionally, the magnetic hyperfine interactions produced by the uneven mass number A nuclei 29Si, 77Se and 125Te were observed, yielding first determinations of the corresponding nuclear spin-rotation coupling constants.