Process time—temporal domain

Under the diffusive laminar flow conditions, the ability to add reagents at specific locations or times leads to the unique ability to control and monitor the spatial and temporal domain of dynamic chemical processes. This attribute has some analogies with the control exerted on biochemical reactions by the micron-scale structures of living cells. Ex-... 

A number of laser based temporal domain experiments have evolved in the past two decades which have no equivalents in conventional spectroscopic technique as they exploit the coherence inherent to stimulated sources. The origin of these methods traces directly to techniques which are widely utilized in NMR and ESR spectroscopy to determine various relaxation and dephasing times. In fact, much of the terminology from magnetic resonance processes has been carried over to laser driven coherent transient studies. See Shoemaker (1978), Levenson (1982) and Brewer and DeVoe (1984). 

In the time or temporal domain, periodicity in operation is incorporated to realize all four principles of PI. A combination of adsorption-reaction-desorption on catalyst surface by periodic forcing of temperatures and pressures demonstrates the application of first principle. Oscillatory baffled flow reactor enhances uniformity, and illustrates the second PI principle. The application examples for third and fourth PI principles are pulsation of feed in trickle bed reactors enhancing the mass transfer rates, and flow reversal in reversed flow reactors shifting the equilibrium beyond limitations respectively. Switching from batch to continuous processing also result in realization of second and third PI principles. 

Fig. 9 A crossbeam two-photon two-color scanning laser microscopic system. Pulses from two beams split from an identical laser output should overlap in both time and temporal domains so that a TPA process could be launched by simultaneously absorbing two photons. Removal of the frequency shifter gives rise to a degenerative two-photon fabrication system...

At present we are far from an understanding of the protein folding process. Even numerical methods as e.g. molecular dynamics simulations do not lead to realistic predictions. Experiments on the folding process have been performed initially on the millisecond time-scale. It was only recently that new techniques - temperature jump or triplet-triplet quenching experiments - allowed a first access to the nanosecond time domain [2-4]. However, the elementary reactions in protein folding occur on the femto- to picosecond time-scale (femtobiology). In order to allow experiments in this temporal range we developed a new... 

Dual to prediction in time domain (with the result of flattening the spectrum of the residual), applying a filtering process to parts of the spectrum has been used to control the temporal shape of the quantization noise within the length of the window function of the transform [Herre and Johnston, 1996],... 

The technique of up-conversion photoluminescence allows one to record the transient PL of a system at the temporal resolution of the laser pulse. It is used to study very fast processes below the picosecond time domain. A typical set-up for this experiment is shown in Fig. 3. The sample is excited at frequency uq by a femtosecond laser pulse and its PL at ujj- is mixed with that of an optically... 

Equations (27) and (28) or alternatively Eq. (31) provide the most general formal expression for any type of 4WM process. They show that the nonlinear response function R(t3,t2,t 1), or its Fourier transform (cum + a>n + (oq,com + tu ,aim), contains the complete microscopic information relevant to the calculation of any 4WM signal. As indicated earlier, the various 4WM techniques differ by the choice of ks and ojs and by the temporal characteristics of the incoming fields E, (t), E2(t), and 3(t). A detailed analysis of the response function and of the nonlinear signal will be made in the following sections for specific models. At this point we shall consider the two limiting cases of ideal time-domain and frequency-domain 4WM. In an ideal time-domain 4WM, the durations of the incoming fields are infinitely short, that is,... 

In conclusion, in this section we presented the formal expressions for the absorption lineshape [Eq. (70)] and for spontaneous Raman and fluorescence spectroscopy. For the latter, we derived Liouville space expressions in the time and the frequency domain [Eqs. (74) and (75)], an ordinary correlation function expression [Eq. (76)], and, finally, the factorization approximation resulted in Eqs. (77) and (78). The factorization approximation is expected to hold in many cases for steady-state experiments and for time-resolved experiments with low temporal resolution. It is possible to observe a time-dependent shift of spontaneous emission lineshapes using picosecond excitation and detection [66-68]. This shift arises from the reorganization process of the solvent and also from vibrational relaxation that occurs during the t2 time interval. A proper treatment of these effects requires going beyond the... 

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