Studies of valence shell photoionization of Cl_2

Abstract

We report photoionization cross sections and photoelectron angular distributions for the 5σ_g , 2π_u and 2π_g orbitals of Cl_2 from threshold to ∼20 eV photoelectron energy obtained using Hartree–Fock photoelectron orbitals. These studies were motivated by recent (2+1) resonance enhanced multiphoton ionization (REMPI) experiments via the 2 ^1Π_g (2π^3_g 4sσ_g ) state which show strong non‐Franck–Condon effects in the ion vibrational distribution suggesting that shape and/or autoionizing resonances may play a role near threshold. Previous single‐photon experiments on the valence orbitals of Cl_2 do not give a consistent picture of these cross sections at low energies. Our results show that there is a shape resonance in the kπ_u continuum. However, preliminary studies show that these π_u cross sections have almost no dependence on internuclear distance and could not be the cause of non‐Franck–Condon effects observed in the REMPI experiments.

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