Anion photoelectron spectroscopy and high level ab init io calculations of the halide -acetylene dimer complexes

Anion photoelectron spectra are presented for the halide-acetylene complexes, X– · · · C2H2 where X = Cl, Br, and I. Electron binding energies are determined to be 4.1, 3.8 and 3.4 eV respectively. Results from CCSD(T) calculations are presented for the neutral halogen-acetylene complexes. Two minima are predicted corresponding to a linear C∞v and T-shaped C2v geometry, with the T-shaped geometry stationary point predicted to be the global minimum. The form of the photoelectron spectrum is determined via prediction of the Franck-Condon factors linking the anion and neutral states. ∗Author to whom correspondence should be addressed.