Pulsed external field, second-harmonic

Fig.3 - 3-BCMU films obtained by evaporation of the solvent (thickness lym). Evolution of the second harmonic intensity under the laser pulses (100 yj/ pulse focal length 50 cm pulse frequency f = 10 Hz boxcar integration time T = 100 ms). The film was always submitted to the laser pulses the external field (E = 10 Vcm was suddenly switched on or off through the HV relay.

Introduction and experimental techniques. In previous sections we drew attention to the fact that, in both the classical and quantum theories, expressions derived for the intensity of resonance fluorescence from atoms subjected to an external magnetic field, equations (15,3) and (15.23) respectively, contain terms which may lead to a modulation of the intensity at the Larmor frequency or its second harmonic. This radio-frequency modulation has been observed in several different kinds of experiment, the simplest of which makes use of pulsed excitation and time-resolved detection of the fluorescent light. 

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