Photodetachment spectroscopy of the C_2nH~- (n = 2-4) anions in the vicinity of their electron detachment threshold

摘要

The electronic spectra of the C_2nH(D)~-, n = 2-4, anions have been observed in the gas phase using photodetachment spectroscopy. These are assigned to ~1#PI# < - X ~1#EPSLON#~+ electronic transitions. The ~1#PI# excited states possess a dipole bound character indicated by the energetic proximity between the origin of the transitions and electron affinities. The dipole states are related to the X ~2#PI# ground states of C_6H and C_8H whereas for C_4H, which has an X ~2#EPSILON#~+ ground state, the ~2#PI# is an excited state. Vibronic coupling through a bending motion of the carbon skeleton is inferred to be the reason of the stabilization of this state.