Studies of metal hydrosulfides III: The millimeter/submillimeter spectrum of BaSH (X̃² A′)

The pure rotational spectrum of BaSH was measured, proving that this molecule has a bent geometry and C_s symmetry, in analogy to the other alkaline earth hydrosulfides. The barium species appeared to be other slightly more bent than the SrSH and CaSH, with a bond angle near 88°. Perturbations resulting from accidental degeneracies of the spin-rotation levels were observed, shifting certain transitions from the expected pattern. Higher K_a components in BaSD were also perturbed. The spin-rotation constants in the barium species were found to contain large second order contributions.