Fluorescence spectrum decaying atomic transitions

Another area of interest in quantum interference effects, which has been studied extensively, is the response of a V-type three-level atom to a coherent laser field directly coupled to the decaying transitions. This was studied by Cardimona et al. [36], who found that the system can be driven into a trapping state in which quantum interference prevents any fluorescence from the excited levels, regardless of the intensity of the driving laser. Similar predictions have been reported by Zhou and Swain [5], who have shown that ultrasharp spectral lines can be predicted in the fluorescence spectrum when the dipole moments of the atomic transitions are nearly parallel and the fluorescence can be completely quenched when the dipole moments are exactly parallel. 

The spectrum below is recorded in fluorescence from a collimated cesium atomic beam, excited on the D F transition by a single mode tunable dye laser. The D level is populated in cascade decay from the P state, which is excited with a broadband CW dye laser. The Fabry-Perot fringes at the bottom correspond to a free spectral range of 50 MHz. 

Photoluminescence (PL) is the emission of light from a material following its illumination. The frequencies of both absorption and emission in luminescence are determined by the transitions between the electronic states, i.e., they correspond to the visible, or close to it, region of the spectrum. The rapidly decaying luminescence typical for atoms and molecules is usually called fluorescence. The lifetime, t, of an excited electronic state can be represented as originating from two competitive channels, radiative versus nonradiative, as... 

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