Rotational spectra and hyperfine constants of ZrO and ZrS

The pure rotational spectra of ZrO and ZrS have been recorded using cavity Fourier transform microwave spectroscopy in the frequency range 9-26 GHz. T he molecules were generated by laser ablation of a solid Zr rod in the pres ence of 0.05% of O-2 or H2S, respectively, in either argon or neon. Rotatio nal spectra of five previously unobserved isotopomers of ZrO in the X(1)Sig ma(+) state have been measured. Spectra for all five (ZrS)-S-32 isotopomers and for the (ZrS)-Zr-90-S-34 isotopomer in natural abundance have also bee n measured; this is the first report of pure rotational transitions for ZrS . Transitions in several excited vibrational states were also measured for the most abundant isotopomers of both species. Atomic mass-dependent Born-O ppenheimer breakdown correction terms were determined by fitting the data o btained for each molecule to a Dunham-like expression. Values for the equil ibrium bond lengths of the two species were also calculated from the result s of these fits. For both the (ZrS)-Zr-91-S-32 and (ZrO)-Zr-91-O-16 isotopo mers, nuclear hyperfine structure due to the zirconium nucleus was observed and values for eQ(q0) (Zr-91) and C-I (Zr-91) have been determined. A rota tional transition in the low lying a (3)Delta state of ZrS has also been ob served. (C) 1999 American Institute of Physics. [S0021-9606(99)00121-X].