MOLECULAR GEOMETRY AND PREDISSOCIATION TIMES IN THE $\tilde{A}^{1}A''$ ELECTRONIC STATE OF HCN AND DCN

$^{1}$G. A. Bickel and K. K. Innes, Can. J. Phys. 62, 1763-1774 (1984). $^{2}$Y. C. Hsu, M. A. Smith, and S. C. Wallace, Chem. Phys. Letters 111, 219-225 (1934).Author Institution: Department of Chemistry, State University of New York at BinghamtonMerging of the vibrational structures of the $\bar{A}$ and $\bar{B}$ electronic states of HCN and DCN into a single $A{-1} A^{\prime\prime}$ $state^{1}$, and new measurements of rotational fine structure between 1600 and 1950 {\AA}, have made it possible to attempt refinement of the molecular geometry in the $\overline{A}$ state; an attempt based on rotational constants of HCN, DCN, $D^{13}CN$ and $DC^{15}N$ will be described. The fine structure is mostly predissociated so that the rotational constants were determined by computer simulation of $K_{v}^{1}$ sub-band contours; in the simulation process it was convenient to measure and analyze also the line-widths of unblended lines in each simulated $K_{0}^{1}$ sub-band. It was then straight forward to estimate $\tilde{A}$-state lifetimes of the DCN’s and their variations with vibrational quantum numbers. These lifetimes range from 120 to 0.4 ps; they will be compared with recently $published^{2}$, directly measured lifetimes for lower vibrational levels of the $\overline{A}$-states of HCN and DCN