A theoretical study on the ionic states with analysis of vibrational levels of the photoelectron spectrum of formaldehyde (CH2O)

A b initio calculations are performed to study the molecular equilibrium structure and the vibrational levels of the low-lying four ionic states, 1 2B2, 2B1, 2A1, and 2 2B2 of formaldehyde (CH2O). The theoretical intensity curve obtained by the Franck–Condon factors for the ionization transitions are also reported and compared with the photoelectron spectrum of CH2O. A number of new assignments of the vibrational levels of the photoelectron spectrum are proposed.