A study of the first ionization potential of the CrO(X5Π) molecule with high-temperature photoelectron spectroscopy

Abstract

The first band in the He I photoelectron spectrum of the CrO(X⁵Π) molecule, obtained via the gas-phase reaction Cr + O₃, has been recorded. The adiabatic and vertical ionization potentials of the observed band were measured as 7.85 ± 0.02 and 8.16 ± 0.01 eV, respectively. Analysis of the observed vibrational structure yielded w_e= 640 ± 30 cm^–1 and Franck–Condon analysis of the vibrational envelope gave r_e= 1.79 ± 0.01 Å for the ground electronic state of the ion, which is predicted on the basis of ab initio configuration-interaction calculations to be a ⁴σ^– state.