Molecular Rydberg states and ionization energy studied by two-photon resonant ionization spectroscopy

In this article, I will review the excited valence/Rydberg states and ionization energies of vinyl chloride, propyne, and allyl radical that we have examined recently in our laboratory by 2+1 resonance enhanced multiphoton ionization (REMPI) spectroscopy. In these studies, we have emphasized spectroscopic investigations from the first excited electronic states to the first ionization energies of the molecules and radicals of interest. In spectroscopic analysis, successful electronic identifications have been facilitated with theoretical (ab initio and density functional) calculations. In particular, we have applied calculated Franck-Condon factors to assist vibrational assignment for experimental vibronic spectra. The spectroscopic studies of these polyatomic excited valence/Rydberg states help us to illuminate the photodissociation pathways and to manifest the complicated chemical-reaction mechanisms due to the multi-dimensionality in polyatomic molecular potential energy surfaces.