THE $\widetilde{A}^{1}A^{\prime \prime}$ EXCITED ELECTRONIC STATE OF HCN: ISOTOPIC EVIDENCE THAT UNIFIES EXPERIMENT AND THEORY

$^{1}$G. Herzberg and K.K. Innes, Can. J. Phys., 35, 842-879 (1957). $^{2}$G.M. Schwenzer, C.F. Bender and H.F. Schaefer, Chem. Phys. Lett., 36, 179-182 (1975).Author Institution: Department of Chemistry, State University of New York at BinghamtonHigh resolution vacuum ultraviolet absorption spectra of $D^{13}CN$ and $DC^{15}N$ are photographed, especially for comparison with the so called $\beta$-X system, observed previously only for $DCN.^{1}$ Isotopic shifts establish the absolute vibrational numbering for this system yielding its assignment to the $\widetilde{A}^{1}A^{\prime \prime}-\widetilde{X}^{1}\Sigma^{+}$ transition. The measured bands between 53200 and $65100 cm^{-1}$ are thereby accommodated by a single electronic transition as predicted by $theory.^{2}$ New vibrational constants of the $^{1}A^{\prime \prime}$ state are presented for DCN as well as for the two heavier isotopes