Knowledge Bank

Vibrational levels with $\nu$ $\ge$ 2 of the low-lying electronic status of the alkaline earth monohydroxides have proven difficult to access owing to Franck-Condon factors that strongly favor the $\Delta \nu =0$ sequences. It has been found, however, that the use of selective detection of fluorescence permits the observation of weak $\Delta \nu 2=1,2,\dots$ transitions. The $B2\Sigma +(02\circ 0)\to X2\Sigma +(02\circ 0)\to X2\Sigma +(02\circ 0)$ transitions of SrOH have been observed by means of laser excitation and resolved fluorescence, respectively. Molecular constants from the rotationally analyzed spectra have been obtained by least-squares fitting. These results and those from preliminary observations of other excited vibrational levels of the bending mode will be described.