THE MILLIMETER AND SUB-MILLIMETER SPECTRUM OF THE BAOH RADICAL

The pure rotational spectrum of the X2SIGMA+ ground electronic states of the BaOH and BaOD radicals has been observed using millimeter/sub-millimeter direct absorption spectroscopy. The lesser abundant isotopically substituted species, (BaOH)-Ba-136 and (BaOH)-Ba-137, have been detected as well. The radicals were created by reacting barium metal vapor, produced in a Broida-type oven, with either H2O2 or D2O2. The rotational and spin-rotation constants were determined for the molecules from a nonlinear least-squares fit to the data, using a 2SIGMA Hamiltonian. Hyperfine constants were also derived for (BaOH)-Ba-137, the one species where hyperfine structure was resolved. These measurements confirm a linear structure for BaOH.