SYMMETRIES, PROPENSITY RULES, AND ALTERNATION INTENSITY IN THE ROTATIONAL SPECTRUM OF N2(C3-PI-U) EXCITED BY METASTABLES AR(3P0,2)

We have obtained high resolution spectra N2(C 3Πu→B3Πg) afterglow fluorescence resulting from excitation transfer from state selected Ar metastable 3P0 or 3P2. This was achieved by selective depopulation of one metastable by optical pumping using a tunable c.w. dye laser. Relative probabilities of excitation of well defined rotational, spin, and parity molecular Λ doublet substates were obtained for reaction of 14N2 and isotopic 15N 2 with Ar*(3P2) and Ar*( 3P0). A semiclassical model is proposed and found in fairly good agreement with the observed relative yields. The physical bases of the model are justified and imply that (a) spin-orbit interactions are effective during the collision, (b) the plane of rotation of the excited N2 molecule is a plane of symmetry, (c) Λ doublet c states are preferentially populated in the excitation transfer process. © 1980 American Institute of Physics.