ELECTRONIC ABSORPTION-SPECTRA OF CYANO-SUBSTITUTED POLYACETYLENE CATIONS IN NEON MATRICES

The A 2Π←X 2Π transitions and vibrational frequencies in the excited electronic states have been determined for the cyanopolyacetylene cations H-(C≡C)n-CN+ (n=2-6) and NC-(C≡C)n-CN+ (n=1-5). The spectroscopic information was derived by absorption measurements after cations from a mass selected beam were condensed together with excess of neon to form a 5 K matrix. Spectra have been also obtained for ions with odd number of π-centers and are tentatively assigned to H-C2n-1-CN+ (n=3-6) and NC-C 2n-1-CN+ (n=3-5). The assignments are based on trends observed for the homologous series of these cations, known gas phase data on three of the smaller species, and the free electron molecular orbital model. © 1995 American Institute of Physics.