Temporal broadening

The EPS experiments were carried out according to the procedure described in Ref. [20], The sample, used in experiments, was a 0.6 M solution of HDO molecules in heavy water at room temperature (maximal OD-O.6). The solution was pumped through a sapphire nozzle to form 100-pm thick, free-standing jet, that was positioned at the intersection of the laser beams. Use of the free-standing jet instead of a sample cell allowed us to avoid unwanted complications such as temporal broadening of the ultrashort pulses, their adverse scattering, and cross-phase modulation. The excitation pulses were -70 fs in duration and centered around -3 tm [19]. The excitation pulse spectra and the absorption spectrum of the OH-stretch vibration of HDO molecules in D2O are shown in the inset to Fig.lb. 

The beam was passed through a pulse picker (4). In order to compensate pulse broadening ( chirp ) introduced by the pulse picker and to precompensate that caused by other bulky optics (lenses, polarizers etc.), the beam was passed through a group velocity dispersion compensation line (5), consisting of a pair of Brewster prisms and a mirror [20], The temporal width of the pump and probe pulses was checked with a fringe-resolved... 

This model predicts that the sum of the exponents of the current decay before and after tT will be 2. As a tends to zero, the temporal distribution j/(2) broadens and the sharp knee seen in Fig. 8.25(b) becomes much less prominent, since the rate of decay of the current is similar both before and after tT. tT will depend on the ratio of the sample thickness to the average displacement of the carrier in the field direction during its random walk through the sample. Use cjf the formal definition of mobility, Equation (4.2), leads to the result that the mobility has a dependence on electric field and sample thickness, L, of the form ... 

The exploitation of the link between IVR and spectral broadening by several groups utilizing jet specroscopic techniques has provided a good deal of information pertinent to IVR and has catalyzed tremendous activity in the field. Nevertheless, there are limitations to time-integrated techniques in revealing the full details of IVR processes. The limitations pertain particularly to the determination of (1) IVR rates, (2) the temporal characteristics of IVR, (3) the coupling matrix elements involved, and (4) the extent of the process. In... 

---