Energy-dependent cross sections for quenching of Na(3p 2P) by several gases

The lifetime of Na(3p 2P) atoms, in the presence of various quenching gases (H2, D2, N2, CO, CO2, and C2H4), has been directly determined by the single-photon time-correlation method. Na(2P) atoms were produced with varying amounts of translational energy by photodissociation of NaI with light of wavelengths 215--240 nm. The large cross sections obtained, and their inverse dependence on relative collisional energy, are best explained on the basis of a ''harpooning'' mechanism, in which a strongly attractive ionic state provides the coupling between upper and lower covalent states