Coherent Response Signals

MRI (ID profiles) of objects with dipolar-broadened spectra was demonstrated by using soft excitation pulses. Long-lived coherent response signals... 

A. K. Khitrin, V. L. Ermakov, and B. M. Eung Coherent response signals of dipolar-coupled spin systems, Z. Naturforsch 59a, 209-216 (2004). 

Note that the application of the convolution scheme in the simple form (44) requires that the nonlinear polarization contains only a single interaction with the probe laser field. Apart from the transient transmittance spectrum considered above, this condition is also fulfilled for related detection schemes such as time-resolved fluorescence, ionization, and excited-state absorption. Coherent spectroscopic signals such as the photon-echo, on the other hand, contain two interactions with the probe laser field, thus requiring the calculation of the full three-time response function, followed by a double convolution. 

Recently, we have found that long and weak radio-frequency pulses can excite very sharp proton NMR response signals in liquid crystals [9]-[ll]. For 5CB, as an example, the linewidth of the coherent long-lived collective response signal can be as narrow as 12 Hz. 

Figure 8.5 Interferometric two-pulse correlation measurements of the coherent response of spots A-D in Figure 8.4. Measurements of the 2PP signal intensity at each hot spot reflects the coherent SP polarization dynamics, near zero delay, as well as a contribution from the sequential 2PP, which is responsible for the slow decay of the signal after the coherent oscillations have died out. The enlarged image of the coherent oscillations shows the SP mode specific nonlinear polarization dynamics. The corresponding laser phase is also shown. ...

As illustrated earlier in the text (Figure 10.5), molecules released from the centrifuge generate an oscillatory Raman signal, characteristic of the coherent rotation with well-defined relative phase relation between the quantum states inside a rotational wave packet. Time-resolved coherent Raman response from a wave packet centered at A = 69 in oxygen is plotted at the bottom of Figure 10.9a. Knowing the wave packet composition from the state-resolved detection discussed above. 

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