Photodetachment spectroscopy of the C 2 nH À „ n Ä 2 – 4 ... anions in the vicinity of their electron detachment threshold

The electronic spectra of the C2nH~D! , n52 – 4, anions have been observed in the gas phase using photodetachment spectroscopy. These are assigned to 1P←X S electronic transitions. The P excited states possess a dipole bound character indicated by the energetic proximity between the origin of the transitions and electron affinities. The dipole bound states are related to the X P ground states of C6H and C8H whereas for C4H, which has an X S ground state, the P 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. © 2002 American Institute of Physics. @DOI: 10.1063/1.1451248#