Electronic absorption spectrum of HC7O

Vibrationally resolved electronic absorption spectrum of 1-oxohepta-2,4,6-triyn-ylium cation has been recorded in a 6 K neon matrix after mass-selected deposition of m/z=101 cations produced from the 1,2,3,4,5-benzenepentacarboxylic acid in an ion source. The band system with origin at 278 nm is assigned to the 2(1)Sigma(+) <- X-1 Sigma(+) transition of the linear-HC7O+ isomer on the basis of theoretical calculations. Vibrational analysis of the electronic spectrum is consistent with the structure. [GRAPHICS] .