Nonadiabatic couplings among states of a colliding pair of atoms or molecules have an essential role in determining state- specific cross-sections for a wide range of elastic and inelastic collision processes. These include nonradiative electronic transitions such as quenching or fine-structure transitions, coherence transfer and collisional depolarization, and rotational and vibrational energy transfer. Nonadiabatic effects are also important in photofragmentation processes such as photodissociation, photoionization, or collisional redistribution of light. Experimental studies of effects of nonadiabatic couplings on the dynamics of optical collisions between alkali (sodium and lithium) and rare gas atoms will be carried out. Both fine-structure branching and the production of Zeeman multipoles will be investigated, along with the recently observed nonlinear laser intensity dependence of the fine-structure branching. An investigation of the LiHe and NaHe molecular Rydberg spectrum, which should exhibit significant rotational nonadiabaticity through the core rotation and vibration, will also be pursued.
