Fourier transform microwave spectroscopy of aluminum hydrosulfide, AlSH

Pure rotational transitions of three isotopic species of aluminum hydrosulfide, AlSH, have been measured with a cavity pulsed jet Fourier transform microwave spectrometer. AlSH was prepared by the reaction of laser ablated Al metal with H2S, and was stabilized in pulsed supersonic free jets of Ar. For each species the transition 101-000 was measured; hyperfine structure due to the nuclear spin of 27Al was observed for the first time and analyzed. For Al32SH and Al32SD, the rotational constants are in excellent agreement with published values. For the third species, Al34SH, this is the first observation, and its rotational constants are consistent with the published geometry. Information on the electronic structure of the molecule has been obtained using the 27Al nuclear quadrupole coupling constants and nuclear spin-rotation constants. The latter have been used to evaluate 27Al NMR shielding parameters, which are compared with those of other 27Al compounds. These shieldings have been found to be in excellent agreement with theoretical predictions. The results should also help facilitate astrophysical searches for the molecule.