Experimental and theoretical studies of the quenching of Li(3p,4p) by N2

Quenching mechanisms of the Li3p and Li4p states in collision with the nitrogen molecule are studied by laser-induced fluorescence spectroscopy and by a quantum chemical calculation. The Li3p state is observed to be efficiently quenched to the Li3s state detected as intense 3s-->2p emission. The Li4p state is efficiently quenched to the Li4s and Li3d states detected as 4s-2p and 3d-2p emissions, respectively. The potential-energy surfaces for the Li(2s-4p)N2 states show a large number of conical intersections and avoided crossings resulting from the couplings between the ionic [Li+(N2)-] and covalent configurations. There are a large number of stable excited states, and we give here the spectroscopic constants for the lowest two stable isomers correlating to Li2p+N2.

Energy transfer in Li(4p) + (Ar,H2,CH4) collisions

The direct collisional energy transfer processes of the excited states of Li(4p) by several gases are investigated under gas cell conditions. The nonreactive absorption profiles of the collision complex are monitored as a function of laser detuning from the Li(2s-4p) resonances. Pronounced structures in the absorption spectra along with high level ab initio calculations of the relevant potential energy surfaces are used to understand the experimental results.

STATE-RESOLVED COLLISION-INDUCED ELECTRONIC TRANSITIONS

▪ Abstract  Laser and molecular beam techniques have enabled researchers to determine the rovibrational levels populated in collision-induced electronic transitions from specified initial levels of several diatomic molecules. As exemplified by the N2+– and CN–rare-gas systems, such measurements, in combination with theoretical calculations of cross sections for these state-to-state collisional processes, provide a means to understand in detail the dynamics of these electronic quenching and energy transfer processes. The present article reviews state-to-state studies of collision-induced electronic transitions. The various collision systems studied provide examples of both perturbation-assisted “gateways” between the initial and final electronic states and perturbation-independent transitions enabled by nonadiabatic mixing induced by the collision partner.