The formation of fluorescent and metastable fragments by photoexcitation of somediatomic molecules in the vacuum ultraviolet region

Abstract

The formation of fluorescent and metastable fragments from four diatomic molecules,i.e. O2, N2, NO and CO, has been investigated in the vacuum ultraviolet region. The neutralparticles are detected by using a microchannel plate stack, where retardingelectric potentials prevent charged particles from reaching the detector. Everydiatomic molecule investigated here shows the formation of fluorescent andmetastable fragments in particular photon energy regions. Three Rydberg states ofO2 convergingto O2+(a 4Πu) undergo both neutral dissociation processes forming fluorescent[O+(4S)]3s 3S1 andmetastable [O+(4S)]3s 5S2; the yield curve for each fragment is determined. Direct and cascade formation of the fluorescent[N+(3P)]3s 4P fragmentfrom N2 are separated, and it is found that the dissociation of the4s σ Rydberg state convergingto N2+(C 2Σu+) preferentiallyproduces [N+(3P)]3p fragments,but not or weakly the [N+(3P)]3s 4P fragment. High -n Rydbergstates converging to NO+(c 3Π) and CO+(D 2Π) undergo neutral dissociation described by the core ion model, resulting in large peaks forneutral particle formation.