A theoretical study of two-color photoionization and autoionization of molecules

The main purpose of this paper is to apply the density matrix formalism for treating multiphoton ionization of multirovibronic level systems. Both direct photoionization and photoionization through autoionization states are taken into account. Numerical results will be presented for demonstrating the effect of the interference resulting from the neighboring rovibronic levels. The theoretical results are applied to interpret two sets of experimental data on two-color photoionization of molecules; one set is for two-color threshold photoionization spectra of jet-cooled aniline which exhibit autoionizing Rydberg structures and the other is for high resolution Rydberg spectra of H₂ by stepwise resonance two-photon ion-pair (H⁺ + H⁻) production.