Pp. Corso et al., THE ROLE OF HYPER-RAMAN TRANSITIONS IN THE RADIATION SPECTRUM OF A STRONGLY DRIVEN 2-LEVEL ATOM, J. mod. opt., 44(4), 1997, pp. 819-830
Numerical results are presented on the spectrum of the light scattered
into the vacuum modes by a two-level atom driven by a strong ramped f
ield of frequency smaller than the natural atomic frequency. The atten
tion is focused on the role of the hyper-Raman part of the spectrum, w
hich is shown to decrease dramatically with increasing ramp time. It i
s suggested that this may explain lack of experimental observation of
the hyper-Raman lines. For zero ramp time, the numerical intensity of
both high-order harmonics and hyper-Raman peaks is shown to agree sati
sfactorily with previous analytical predictions except in the region o
f overlap of the two series of peaks. This lends support for the sugge
stion that the plateau in the spectrum is related to quantum-mechanica
l interference between high-order harmonics and hyper-Raman processes.
There is also good agreement between the numerical amplitude of the p
lateau and previous analytical predictions. A physical mechanism for t
he cut-off frequency which terminates the plateau, based on approximat
e energy conservation in hyper-Raman transitions, is presented and is
shown to be in agreement with present numerical and previous analytica
l results.