Gas phase electronic spectra of the carbon chains C5, C6, C8, and C9

Three electronic absorption systems for C-5 at 511, 445, and 232 nm and one for C-6, C-8, and C-9 centered at 228, 259, and 288 nm have been observed in the gas phase. The C-5 chain was produced in both discharge and ablation sources and detected using resonant two-color two-photon ionization spectroscopy involving 10.5 eV photons. The decay of the excited singlet electronic states indicates fast intramolecular processes on a subpicosecond time scale. The internal energy is assumed to be trapped in a triplet state for at least 15 mu s. Hole-burning experiments on the 2 (3)Sigma(-)(u)<- X (3)Sigma(-)(g) transition of C-6, C-8, and (1)Sigma(+)(u)<- X (1)Sigma(+)(g) of C-9 confirm the predissociative nature of the excited electronic states.