ELECTRONIC ABSORPTION-SPECTRA OF LINEAR CARBON CHAINS IN NEON MATRICES .3. HC2N+1H

The electronic absorption spectra of HC2n+1H and HC2n+1H+ (n=2-7) in n eon matrices have been obtained. The species were prepared by codeposi tion of mass selected HC2n+1H+ ions with neon at 5 K. For each species the O-0(0) band of the electronic transition as well as frequencies o r fundamental vibrations in the excited state have been determined. Th e wavelength of the origin band in this homologous series is linearly dependent on the number of carbon atoms. Isotopic labeling supports th e vibrational assignment and confirms the presence of two equivalent h ydrogen atoms for HC2n+1H and HC2n+1H+ Based on spectroscopic consider ations, a linear geometry is assumed with one hydrogen atom located at each end, and that the observed spectra of HC2n+1H are their 3 Sigma( u)(-) <-- X (3) Sigma(g)(-) transition. (C) 1995 American Institute of Physics.