Bulletin of the American Physical Society
Coherent population transfer and application in collision dynamic studies
Klaas Bergmann
Abstract
Techniques for population transfer are needed to gain more complete insight into the collision dynamics of thermally unpopulated levels, e.g. highly vibrationally excited states of molecules. Very promising new techniques are now becoming available. They invoke coherence properties of the radiation field and rely on the phenomena of adiabatic following. In this presentation, I will discuss one of them, the STIRAP method, which induces efficient and highly selective flow of population from an initially populated level 1 to a final level 3. These levels are coupled by a pump and a Stokes laser, with both laser frequencies tuned to resonance with an intermediate level 2. Despite the resonance, spontaneous emission, which may populate levels other than level 3, is eliminated. The method can be implemented with cw as well as with pulsed lasers. First results from a study of the effect of initial vibrational excitation of a molecule on a chemical reaction will be presented. It will also be shown how this technique allows the orientation of electronic or molecular angular moments. The prospects of using this technique for efficient transfer of photon momenta to an atom may be mentioned.