Elimination and migration of hydrogen in the vacuum-ultraviolet photodissociation of pyridine molecules

Elimination of the excited hydrogen atoms H( n ), n = 4-7, and hydrogen migration in formation of the excited NH( A 3 ?) free radicals in the photodissociation of pyridine, C 5 H 5 N, molecules have been studied over the 17.5-70 eV photon energy range. In the measurements the photon-induced fluorescence spectroscopy technique has been applied. Both fragments are produced through excitation of pyridine molecules into higher-lying superexcited Rydberg or doubly excited states. The mechanisms for fragmentation of pyridine into H( n ) and NH( A 3 ?) are discussed. Ab initio quantum chemical calculations have been performed to elucidate the hydrogen migration mechanism in the NH formation, which is not a self-contained unit in the structure of pyridine.