Anion photoelectron spectroscopy of C5H

Anion photoelectron spectroscopy is performed on the C5H− species. Analogous to C3H− and C3D−, photodetachment transitions are observed from multiple, energetically close-lying isomers of the anion. A linear and a cyclic structure are found to have electron binding energies of 2.421±0.019eV and 2.857±0.028eV, respectively. A cyclic excited state is also found to be 1.136eV above the linear Π2C5H ground state. Based on our assignments of the observed transitions and previous calculations on the energetics of neutral C5H isomers, the cyclic A11 anion state is found to lie 0.163eV below the A3 linear anion.