Collisions Involving Molecules in High Vibrational States

4 Collisions Involving Molecules in High Vibrational States 

Molecules in high vibrational levels n) of the electronic ground state generally show much larger collision cross sections. If the kinetic energy Ekin of the collision partners exceeds the energy difference (Ed - Ey) between the dissociation 

stimulated emission pumping is a powerful technique to achieve a large population in selected vibrational levels [1046, 1047]. While the pump laser is kept on the transition /) k), the probe laser is tuned to the downward transition A ) u) (Fig. 8.21b). Proper selection of the upper level k) allows one to reach sufficiently large Franck-Condon factors for the transition k) u). With 

With a coherent stimulated Raman process (STIRAP) (see Sect. 7.3), nearly the whole initial population Ni may be transferred into the final level If) [1048]. Here no exact resonance with the intermediate excited level ) is wanted in order to avoid transfer losses by spontaneous emission from level ). The population transfer can be explained by an adiabatic passage between dressed states (that is, states of the molecule plus the radiation field) [1049, 1050]. 

Investigations of collision processes with molecules in these selectively populated levels f) yields the dependence of collision cross sections on the vibrational energy for collision-induced dissociation as well as for energy transfer into other bound levels of the molecule. Since the knowledge of this dependence is essential for a detailed understanding of the collision dynamics, a large number of theoretical and experimental papers on this subject have been published. For more information the reader is referred to some review articles and the literature given therein [1039, 1045, 1051-1053]. 

stimulated emission pumping is a powerful technique to achieve a large population in selected vibrational levels [13.88,13.89]. While the 

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