A combined ab initio and Franck–Condon simulation study of the photodetachment spectrum of the anion

A general analytical expression for the calculation of the two-dimensional four-mode Franck–Condon overlap integrals was presented and applied to scrutinize the photoelectron spectroscopy of ClO 2 - . Geometry optimization and harmonic vibrational frequency calculations have been performed on the X ∼ 2B1 state of ClO2 and X ∼ 1A1 state of ClO 2 - by using the density functional theory (B2PLYP functional) and the coupled cluster singles and doubles with perturbative triples [CCSD(T)] methods with various basis sets up to aug-cc-pVQZ. The adiabatic electron affinity of ClO2 was computed by using the CCSD(T) method extrapolated to the complete basis set limit with aug-cc-pVXZ (X = D, T, Q). Franck–Condon analyses and spectral simulation were carried out on the ClO2( X ∼ 2B1)–( ClO 2 - X ∼ 1A1) photodetachment process. The simulated photoelectron spectrum of ClO 2 - are in accord with the experiment. While the Duschinsky effect plays a minor role and can be neglected. In addition, the equilibrium geometry parameters, R(Cl–O) = 1.572 ± 0.005 Å and ∠ (O–Cl–O) = 112.5 ± 0.5°, of the X ∼ 1A1 state of ClO 2 - , are obtained by employing an iterative Franck–Condon analysis procedure in the spectral simulations.