Time delay from scattering phase

In the time domain, the fluorescence acquires a phase shift and a demodulation, while the scattering does not suffer from a delay. In the frequency domain the phase shift always starts at 0° for low frequencies and tends to 90° in the limit for high frequencies, while the demodulation starts at 1 and tends to 0. However, for the immediate scattering, no phase shift and no demodulation is observed. This is exactly what is used in our approach at very high modulation frequencies, the fluorescence is completely "demodulated" and does not contribute to the measurement signal, that is solely comprised of the not-demodulated scattering. Any HRS measurement at high modulation frequencies will reveal an inherent, fluorescence-free, hyperpolarizability value. 

Fig. 6.13. The polariton wavepacket, created by coherent scattering of picosecond laser and Stokes pulses, propagates in the crystal at the angle 0 with respect to the excitation direction. This angle is determined by the excitation wavevector geometry (see above). The coherent amplitude of the propagating wavepacket may be measured by phase-matched coherent anti-Stokes scattering of a probe pulse suitably delayed in time (fn) and displaced in space (by Xn)- Reprinted with permission from Gale et al. (68). Copyright (1986), American Physical Society.

Figure8.22 Phase portraits of stabilized (a) period-1 and (b) period-2 orbits embedded in a chaotic attractor in the BZ reaction. Scattered points show chaotic trajectory (delay time r = 1.3 s) before stabilization. (c) Time series showing potential of bromide-sensitive electrode. Control via change in input flow rate of cerium and bromate solutions was switched on from 27,800 s to 29,500 s to stabilize period-1 and from 30,000 s to 32,100 s to stabilize period-2. (Adapted from Petrov et al., 1993.)...

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