Resonance Raman spectra of polyyne molecules C10H2 and C12H2 in solution

Resonance Raman spectra of hydrogen-capped linear carbon molecules, polyynes H(-C equivalent to C-)(n)H (n = 5,6), were measured in n-hexane. For C10H2, the peaks at 2123 cm(-1) and 2017 cm(-1) were identified as the nu(3)(sigma(g)) and nu(4)(sigma(g)) modes in D-infinity h symmetry, respectively. For C12H2, the peaks of nu(3)(sigma(g)) at 2097 cm(-1) and nu(4) (sigma(g)) at 2053 cm(-1) were identified. The relative intensities of the first-order Stokes lines and their resonance enhancement are discussed in terms of the Franck-Condon overlap and resonance absorption relevant to the fully-allowed electronic transition of (1)Sigma(+)(u) <-> (Chi) over tilde (1)Sigma(+)(g). (c) 2006 Elsevier B.V. All rights reserved.