High-speed time-resolved

There are several types of measurements for which standard rapid-scanning interferometers may be inappropriate. These include hyperspectral imaging (Section 14.5), high-speed time-resolved spectrometry (Section 19.2), photoacoustic spectroscopy (Section 20.3), and sample modulation spectroscopy (Chapter 21). For these measurements it is necessary to hold the optical path difference constant while a measurement is made, after which the OPD is rapidly advanced to the next sampling position and then held constant once again for the next measurement. This process is repeated until all the data needed to obtain the interferogram are acquired. Such interferometers are called step-scan interferometers. 

Conventional TCSPC equipment has been successfully employed in LSM for fluorescence spectroscopy on discrete microscopic volumes [18, 19] and for fluorescence lifetime imaging at a low acquisition speed [1], The use of conventional TCSPC equipment for imaging results in very long acquisition times, several to many minutes per (time-resolved) image. Importantly, operating the TCSPC detection system at too high detection rates, above 5% of the excitation frequency, results in distortion of the recorded decay curve [20],... 

Photodiodes occur in many different varieties and are useful in both steady-state and time-resolved fluorescence studies. Photodiodes designed for use in steady-state or on microsecond time-scales are inexpensive and have effective areas up to a few square millimeters, and are capable of efficiently matching to simple focusing optics. However, as the temporal resolution increases so does the cost, and the effective area has to be reduced. For example, APDs with response times in the 50 psec region have effective diameters ofca. 10 /small active area of high-speed devices is currently the primary drawback in fluorescence studies. Also, photodiodes other... 

Per-Anders Persson et al, "A Technique for Detailed Time-Resolved Radiation Measurements in the Reaction Zone of Condensed Explosives , 4thONRSympDeton(1965), 602-08. Preliminary experiments with nonporous 60/40-RDX/TNT and NMe (N it ro me thane) using a fast photomultiplier and high-speed oscilloscope are described. The technique permitted recording... 

Ionization in a Detonation Wave. Hay et al (Ref 9) obtained high-speed framing camera pictures and time-resolved spectrograms of the... 

The reactions in Table 1 are transfer of H, O, N, S, halogen and alkali metal atoms. They are also reactions of atoms (H, O, N, S, halogen and alkali metal atoms) with small molecules. They are exothermic and have high specific rates (low activation energies and normal steric factors). These features are desirable for the study of chemi-excitation. High heat release permits substantial excitation. Small, low moment of inertia product molecules have spectra that may be resolved with moderate power spectrographic and spectrometric instruments. High speed provides the necessary number of reaction acts per unit time. 

Apart from the abovementioned PIV techniques, there are still some other PIV systems designed for the particular purposes. Among them, the time-resolved or dynamic PIV, high-speed scanning PIV, dual-plane PIV, and simultaneous orthogonal-plane PIV are briefly introduced as follows. 

In the earlier publications (1,2) it was shown how hydrodynamic chromatography (HDC) could be applied in the study of polymer latexes to determine particle-size. An improved technique for the HDC was developed which utilized higher efficiency and resolving power columns to significantly reduce the analysis time (3). A high speed integrated computer was included in this improvement so that both particle-size and particle-size distribution of latexes could be quantified in the relatively short period of time. This high speed computerized version of the HDC has been used extensively for measurements on the final latex. 

FIGURE 7-20. High-speed gradient analysis. Column Radial-Pak Resolve Cs, (10 /am), 8 mm ID x 10 cm. Gradient conditions 50-70% THF/H20 using convex curve. Detector UV at 254 nm, 0.5 AUFS. Sample polystyrene MW800. (a) Flow rate 2.5 mL/min run time 30 min backpressure 750 psi chart speed 1 cm/min. (b) Flow rate 5 mL/min run time 15 min backpressure 1500 psi chart speed 2 cm/min. (Reproduced from reference 1 with permission.)... 

The large amount of data which has to be collected in time resolved measurements, especially if full two-dimensional patterns are recorded, leads to the development of dedicated high speed data acquisition systems. This is the third component which is necessary together with the source and detectors, to bring synchrotron radiation X-ray experiments to their full deployment. 

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