Knowledge Bank

In spontaneous Raman scattering both strong and weak transitions occur simultaneously and the intensity of each transition is unaffected by the presence of other transitions. In contrast to this, in stimulated Raman scattering due to the exponential growth of the scattered wave and the subsequent depletion of laser power, generally only the most probable transition is observed. However, competition between stimulated transitions of nearly the same probability can be studied. In gases the degree of competition between Raman transitions can be varied because the vibrational and rotational transition probabilities depend differently on temperature and pressure. Data on the competition between two vibrational transition, two rotational transitions, and a vibrational and a rotational transition will be presented and compared to theoretical predictions.