Laser-induced collisional energy transfer

Abstract

A review of the status of theoretical and experimental work on Laser-Induced Collisional Energy Transfer (LICET) is presented. The process involves two dissimilar atoms, one of which is excited, colliding in the presence of a laser field. If the radiation field is properly tuned to an interatomic resonance, the initially excited system undergoes a transition to its ground state, while its partner gains both the excitation energy and that of a photon. The transfer cannot occur unless both collisional and radiative interactions are present. The line shape of the excitation spectrum, markedly asymmetric, is closedly related to the interaction dynamics. Details of theories applicable to low intensities, as well as their high-field counterparts are discussed, as are the predictions of spectral shapes and comparison with measurements. The treatment is extended to include studies of magnetic-state and electronic-state coherences, allowing an additional insight into the nature of the process. Representative experimental investigations are surveyed, including a detailed description of experimental arrangements specifically designed for high-accuracy spectral measurements. Finally, it is shown how a wider approach to the LICET process, by considering it as a radiative transition of a transient molecule, can be promising for an improved understanding of the problem.