Investigation of the valence ionization spectrum of chromium carbonyl using an ab initio quantum dynamical approach

The nuclear dynamics of the chromium carbonyl cation following an ionization process corresponding to the ²T_2g ← ¹A_1g transition is studied theoretically, for the first time, using a fully quantal approach as well as high levels of the ab initio electronic structure and semiempirical density functional theory (DFT) methods. The photoelectron spectrum is calculated by the construction of a Hamiltonian model, in which the two totally symmetric modes ν₁₉ (the Cr-C stretching mode) and ν₃₉ (the C-O stretching mode) together with the spin-orbit (SO) coupling up to the zeroth-order SO splitting are treated. The potential energy curves along these two vibrational modes are computed by using the DFT. The simulated photoelectron spectrum is found to be in good agreement with the corresponding experimental one, leading to the conclusion that the potential energy surfaces and the diabatic population analysis are accurately determined. Our calculation confirms that the vibrational modes ν₁₉ and ν₃₉ are the vibrational progression of the valence ionization spectrum of the chromium carbonyl cation.