SELENOFORMALDEHYDE: A ROTATIONAL ANALYSIS OF THE $A^{1}A_{2} - \bar{X}^{1}A_{1} 735 nm$ BAND SYSTEM OF H2C78 Se and $H_{2}C^{78}Se, H_{2}C^{80}Se$, and $D_{2}C^{80}Se$ FROM HIGH RESOLUTION LASER FLUORESCENCE EXCITATION SPECTRA

Abstract

High resolution laser fluorescence excitation spectra of vibronic bands in the $A^{1}A_{2} - \tilde{X}^{1}A_{1}$ system of selenoformaldehyde have been observed with Doppler-limited resolution. The results of the rotational analysis of the origin band of $D_{2}C^{80}Se$ and the $4^{1}_{n}$ bands of $H_{2}C^{80}Se$ and $H_{2}C^{75} Se$ will be presented. The electronic transition is shown to be singlet-singlet in nature and the band polarizations are consistent with previous vibronic assignments. Erratic perturbations are observed in all three bands. The derived excited state $r_{\circ}$ structure is similar to that of $H_{2}CS$, suggesting that selenoformaldehyde adopts a near-planar equilibrium structure in the excited state. Some preliminary results of the ongoing analysis of the tripletsinglet system will also be presented