Probe configurations

Returning to the original pump-probe RRS, it is a simple matter to complete the 4WM WMEL diagrams for any proposed RRS. Usually RRS experiments are of the frill quadrature sort, both spontaneous RRS as well as homodyne detected femtosecond RRS. The latter fit most pump-probe configurations. 

Major breakthroughs in early ultrafast VER measurements were made in 1972 by Laubereau et al [22], who used picosecond lasers in an SRS pump-incoherent anti-Stokes Raman probe configuration, to study VER of C-H... 

In a pump-probe configuration, using photodiodes for the detection, significant absorption spectroscopic data are reported in Fig.l. Following the interaction of UV photons with aqueous OH ion, two well defined electronic trajectories are observed in the first 4 ps. 

Fig. 17.4. Typical near-surface oxidation maps as measured in the non-wear and main wear zones, and strain maps as measured in the wear zone of UHMWPE-retrieved acetabular cups (a) 25 years and 3 months exposure in vivo and (b) 17 years and 9 months exposure in vivo. The linear dimensions of the map and the collection depth of the focal plane in confocal probe configuration are also explicitly shown...

The duplex probe configuration provides for a close proximity of the donor/acceptor pair and may lead to two mechanisms of quenching FRET and direct transfer (contact-mediated) quenching [78]. Placement of the fluorophore and quencher toward the centre of the duplex probe sequence may further add to the quenching efficiency as the ends of duplexes are known to breathe and are not as tightly bound as internal base pairs. Duplex probes are relatively easy to synthesize as the fluorophore and quencher moieties do not have to be incorporated into the same strand. 

Typical configurations of laser flash photochemical apparatus for the detection of transients in a timescale longer than 1 ns are shown in Figure 6.8. The pump-probe configurations in Figure 6.8 are used for the front-face and side-on irradiations of the... 

Femtosecond time-resolved methods involve a pump-probe configuration in which an ultrafast pump pulse initiates a reaction or, more generally, creates a nonstationary state or wave packet, the evolution of which is monitored as a function of time by means of a suitable probe pulse. Time-resolved or wave... 

We are interested in measuring the transient absorption spectra of samples at various times after their sudden excitation to higher electronic states. For this purpose a conventional two pulse excite-and-probe configuration is employed, in which interpulse jitter is negligible because the same single amplified laser pulse is the source for both of those used in the measurement. Figure 1 schematically depicts our optical configuration. 

Figure 11.20. Schematic representation of a thermomechanical analyser (a) and (b) with various probe configurations (c)...

In this equation, the subscripts p-pump and s-pump represent the polarization direction of the pump beam, and the values of X 333 and % 3I13 are related to the SH signal of p- and s-probes, respectively. To compare with in the THG experiment (Eq. 12.15), we plot values of these two experiments as a function of a in Figure 12.17. One can clearly see that for both p- and s-probe configurations, the differences between Xp- pump nd X%ump EFISH experiment are much smaller than that of the THG experiment, especially for the s-probe configuration. Consequently, the photoinduced X distribution was observed to be almost isotropic in this particular EFISH experiment. 

Figure 12.26. Spectra of an acetaminophen tablet obtained with different fiber-optic probes, with the same acquisition conditions and plotted on the same intensity scale. Relative intensities indicate probe efficiency. Probe configurations are (a) 6 around I, beveled, 400 um diameter fibers, unfiltered (b) 6 around I flat tipped, 400 pm, unfiltered (c) 6 around I beveled, 400 pm, filtered (d) 6 around 1, flat tipped, 200 pm, unfiltered (e) two-fiber beveled, 400 pm, unfiltered (f) Carrabba and Rauh design (Fig. 12.17) (g) two-fiber, beveled, 4(X) pm, filtered. (Adapted from Reference 15, with permission.)...

The pump-probe configuration provides the classic approach to 2D spectroscopy since it involves two independently tunable frequencies [1]. In NMR the analogous approach is double resonance Fourier spectroscopy. In fact the method... 

Figure 5. Set of time-resolved UV-near-IR spectroscopic data (3.44-0.99 eV) following the femtosecond UV excitation of an aqueous sodium chloride solution ([H20]/[NaCl] = 55). An instrumental response of the pump-probe configuration at 1.77 eV (n-heptane) is also shown in the middle part of the figure. The ultra-short-lived components discriminated by UV and IR spectroscopy correspond to low or high excited CTTS states (CTTS, CTTS ), electron-atom pairs (Che pairs), and excited hydrated electrons (ehyd )- The spectral signature of relaxed electronic states (ground state of a hydrated electron, (ehyd) electron-cation pairs, a e hyd) observed in the red spectral region.

The Du Pont Model 943 TMA module is shown in Figure 11.4. The apparatus uses a LVDT to sense linear displacements of the sample probe. A thermocouple in direct contact with or in close proximity of the sample is used to detect the sample temperature. The sample and probe are surrounded by a temperature-controlled cylindrical heater and Dewar assembly. Various probe configurations allow the apparatus to be used in the expansion, compression, penetration, tension, stress relaxation, parallel plate rheometry, and fiber tension. The temperature range of the instrument is — 180-800°C an optional furnace can be used to extend the range to 1200 C. 

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