Li(2p) excitation by low-energy collisions with H2and N2

Abstract

The study of the Li(2p to 2s) emission induced by collisions with H2 and N2 has supplied: (i) absolute integral cross sections, (ii) the polarisation of the Li(2p to 2s) transition as a function of the relative collision energy (1-600 eV), (iii) differential 2p excitation cross sections and (iv) the components of the Stokes vector for Li(2p to 2s) from photon-scattered-atom coincidence measurements as a function of the scattering angle and the collision energy. The polarisation analysis reveals that mainly the lowest excited molecular state is populated in non-adiabatic transitions. Efficient transitions take place at internuclear distances as large as 2.0 AA for both H2 and N2. From the occurrence of circular polarisation of the coincident photons the authors predict that higher lying states are also collisionally populated to some extent.