Time correlation function pulse echo experiments

S. Mukamel In general, multipulse experiments depend on a multitime correlation function of the dipole operator [1], The term x(n) depends on a combination of n + 1 time correlation functions. Their behavior for large n will depend on the model. In some cases (e.g., the accumulated photon echo used by Wiersma) the multiple-pulse sequence is simply used to accumulate a large signal and the higher... 

In principle, the II and IT interactions could be performed by separate pulses, in which case the time separation of these pulses would become a third time variable t2. This experiment would be the stimulated Raman echo (SRE). During r2, the vibrator would be in a pure state (p in Fig. 3, pm in other pathways), and the dynamics would be governed by the population relaxation decay time Ti. Thus the SRE is a three-dimensional experiment that measures the correlation function... 

An essential point in the quantitative interpretation of the Raman echo is that the two-dimensional Raman echo is really a reduction of the SRE experiment, which is fundamentally three dimensional. In the idealized Raman echo correlation function presented earlier [Equation (10)], the reduction occurs by fixing r2 = 0 in Equation (29). However, in real experiments using pulses with nonzero duration, interactions II and IT can occur at different times within the pulses. Although the observed Raman signal... 

Figure 4 Femtosecond 2D-IR vibrational echo spectrum of (acac)Rh(CO)2 in hexane in the i (CO) region. This is the spectrum obtained when the train of four IR pulses used in the experiment had parallel polarizations. It displays a correlation of vibrational frequencies during two experimentally controlled time periods and the data are plotted as a function of frequencies excited during the evolution (cci) and detection (1 3) periods. Off-diagonal peaks represent anharmonic coupling between the i (CO) modes. (Adapted by permission of the American Institute of Physics from J. Chem. Phys. 2001, 115, 10814-10828.)...

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