Interference effects in step-wise fluorescence due to level-crossings

摘要: The semi-classical derivation of the Kramers-Heisenberg formula describing resonance scattering is extended to step-wise light. We consider an atom (such as 198Hg) which interacts with two polarized beams light (?2537 ? and ?4358 ?): starting from a specific initial state 0 (6 1S0), it undergoes two-step excitation 1S0 6 3P1 7 3S1), makes transition one final F (any magnetic sub-state 3P2.1.0 terms). It thus emits radiation (?5461 or 4358 ?4047 ?). A possible route r r' taken by in process defined intermediate states (r', r). When there are routes connecting F, fluorescent intensity observed through analyser differs that obtained adding corresponding rates, owing quantum-mechanical interference term. Observations on 198Hg vapour function applied field confirm three types interferences, occurring at zero-field crossing Zeeman sub-levels. first analogous fluorescence. Two new (i) level-crossing signal essentially absorption second radiation, due degeneracy excited term 3P1), (ii) multiplicative signal, where mutual coherence between pair degenerate step carried over next step.