Gas-phase electronic spectrum of the C14 ring

The electronic spectrum of a cyclic C-14 in the visible range has been detected in the gas phase by a mass selective resonant two-color two-photon ionization technique coupled to a laser ablation source. Absorption is localized in the 19 000 to 20 000 cm(-1) region and appears as a dozen of 3-7 cm(-1) narrow peaks belonging to one or two close-lying electronic states. Bands have structures which for the narrowest ones is likely to be the rotational profile contour. The spectrum is attributed to a cyclic form Of C-14 based on time-dependent density-functional calculations and reactivity with H-2. The spectral pattern differs from that previously seen in the larger C4n+2 member rings, C-18 and C-22, indicating some sort of a structural crossover.