Efficiency of selective two-stage laser interaction with an atomic beam

The efficiency of a two-stage selective laser interaction with an atomic beam is analyzed on the assumption that the interaction region is uniformly illuminated and the atomic beam is an optically thin layer. It is assumed that there is no spontaneous or field-induced recombination. The analysis is made for three energy levels. Formulas are obtained for the dependences of the efficiency of the interaction on such parameters as the laser radiation intensity, excited-state lifetime, absorption cross section, atomic (molecular) beam velocity, and dimensions of this beam.