Electronic spectroscopy of the (C)over-tilde-(X)over-tilde and (D)over-tilde-(X)over-tilde transitions of BaOH

We report the first observation of the (D)over-tilde(2) Sigma(+)-(X)over-tilde(2) Sigma(+) electronic transition of the free radical BaOH. This molecule was prepared in a supersonic expansion by a laser ablation method and electronic spectra have been recorded using laser-induced fluorescence. The (D)over-tilde-(X)over-tilde spectrum is dominated by a single vibrational progression which has been assigned to the Ba-O stretch in the (D)over-tilde state. The (C)over-tilde-(X)over-tilde system of BaOH, reported in very low resolution work by several other groups, has also been investigated. The spectrum of this system is more complicated than expected by analogy with related molecules, notably BaF. Two band systems, very close to each Ether and each apparently showing a spin-orbit splitting, were observed. Possible explanations for this behaviour are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.