$A^{1}\Sigma^{+} - \bar{X}^{1}\Sigma^{+}$ ELECTRONIC TRANSITION OF YOH IN THE VISIBLE REGION

Abstract

Excitation spectra of the new molecules YOH and YOD have been recorded in the 500-625 nm wavelength region by laser-induced fluorescence, following reaction of laser-ablated yttrium with $H_{2}O$ or $D_{2}O$ under supersonic jet-cooled molecular beam conditions. Rotational analyses of $^{1}\Sigma^{+} - \bar{X}^{1}\Sigma^{+}$ bands near 540 nm at high resolution gave the following substitution structure for the ground state: \[ \tilde{X}\Sigma^{-}: r(Y-O) = 1.948\; {\textrm{\AA}};\; r(O-H) = 0.92_{1} \;\textrm{\AA}. \] Wavelength-resolved fluorescence spectra have given the ground state vibrational frequencies \[ YOH (YOD): \nu^{2},\; bend = 314 (247)\;cm^{-1}; \nu^{3},\; YO\;stretch = 674 (654)cm^{-1} \] No evidence for the $\nu_{1}$ (OH stretch) mode was observed. Very complicated weak structure at the long wavelength end may possibly correspond to a singlet-triplet transition.