Molecular Rydberg States and Ioniza tion Energy Studied by Two-Photon Res o nant Ioniza tion Spectros copy

In this arti cle, I will review the excited valence/Rydberg states and ioniza tion ener gies of vinyl chloride,propyne, and allyl radi cal that we have exam ined recently in our labo ra tory by 2+1 reso nance enhanced multiphoton ioniza tion (REMPI) spectros copy. In these studies, we have empha sized spectroscopic inves ti gations from the first excited electronic states to the first ioniza tion ener gies of the molecules and radi cals of inter est. In spectro scopic analy sis, success ful electronic identi fi ca tions have been facil i tated with theo ret i cal
(ab initio and density functional) calcu la tions. In partic u lar, we have applied calcu lated Franck-Condon factors to assist vibra tional assign ment for exper i men tal vibronic spectra. The spectro scopic studies of these polyatomic excited valence/Rydberg states help us to illu mi nate the photodissociation pathways and to manifest the compli cated chemi cal-reaction mecha nisms due to the multi-dimensionality in polyatomic molec u larpo ten tial energy surfaces.