Nonradiative Energy Transfer in Li(3p)−CH4 Collisions

The direct collisional energy transfer process Li*(3p) + CH4 → Li*(3s) + CH4 is investigated both theoretically and experimentally. We measured the nonreactive far-wing absorption profiles of the LiCH4 complexes by monitoring the Li(3s) → Li(2p) fluorescence at 812.6 nm. The intensity of the Li(3s) → Li(2p) fluorescence decreases with detuning, indicating a more efficient transition rate at low detuning. A high level ab initio calculation in both C 2 v and C 3 v symmetry is performed to provide a general picture of the nonradiative transition induced by collisions between lithium atoms and a methane molecule.