Slow photoelectron velocity-map imaging of the CnH− (n = 5–9) anions

Abstract

High-resolution photoelectron spectra of the CnH− anions with n = 5–9 are acquired with slow electron velocity-map imaging (SEVI). Spectral features are assigned with the help of electronic structure calculations and Franck–Condon simulations. Well-resolved transitions to the linear 2Π and ã4Σ− neutral states are observed for species with an odd number of carbon atoms. For C6H− and C8H−, transitions to the 2Π neutral ground state and the low lying Ã2Σ+ excited state are observed. Precise electron affinities, term energies, fine structure splittings, and gas-phase vibrational frequencies are determined. The C5H−, C7H− and C9H− SEVI spectra are consistent with the anions having 3Σ− linear triplet ground states.