Single flash

2 Experimental Methods for Lifetime Measurements 7.2.1 Single Flash 

Lifetimes shorter than a nanosecond can be measured using picosecond lasers with suitable detectors (streak camera) [3], bearing in mind that, as a rule of thumb, the cost of the equipment is inversely proportional to its time resolution. However, the measurement of lifetimes shorter than a nanosecond is most commonly performed with a single photon apparatus (see Sect. 7.2.3). Lasers with pulse duration shorter than 100 femtoseconds (1 fs = 1 x 10 s) are also available, but with such equipment the sample emission eannot be monitored for technical reasons, and transient absorption must be measured instead (see Chap. 8). 

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Complex Flow Sheets Operating plants do not consist of single flashes, neat exchangers, distilfation towers, or reac tors. As the number of pieces of eqmpment increases within the unit under study, the reconciliation becomes more difficult. For example. Fig. 30-21 presents a more comphcated, three-module unit. 

An effort has been made to present the basic understanding of the method as it applies to systems involving unequal molal overflow, open steam distillation and single flash vaporization in Figures 8-42 and 8-43. 

This circuit is of the single-flash variety that is, usually no attempt is made to sum consecutive pulses electronically. Photographic integration to reduce the noise might be possible, however. A time resolution of a few microseconds is to be expected. 

From Fig. 50 it is apparent that the break in the decay curves is quite an obvious one. However, the long-lifetime component becomes very weak with concentration and could be overlooked if unexpected. Gallagher speculates that the reduced sensitivity inherent in single-flash experiments could lead one to draw the best straight line through the earlier points of greatest intensity. The fact that the water is a very effective quencher and that the dual nature of the decay curves point to the fact that the introduction of a... 

This is the signal from a single experiment, which is a single flash in this case. With the additional assumptions that n0, S, and k are constant from... 

Figure 11. Time resolved spectra obtained from a single flash of a xenon lamp. Total time period (record), 1 msec.

Having calibrated the system the usual procedure is to clamp the flash-gun at the correct distance pointing vertically downwards onto the darkroom bench. The gel, in the cassette, is covered with the film and, in total darkness, exposed to a single flash. The film is overlayed with the intensifying screen and the cassette closed. The cassette is finally stored at -70°C (for optimum quantative accuracy) for the required time. The film should subsequently be developed in total darkness. 

The kinetic mechanism of the OEC was deduced by Bessel Kok (24), who used an oxygen electrode to monitor yields of dioxygen associated with single flashes of light. The OEC exhibits a periodicity in oxygen... 

After vacuum distillation, a residue of 1 to 2 g. is left in the flask. When air is admitted to the flask, a single flash of light sometimes occurs. In one case, the thermometer and stopper were even blown off the flask. The cause was not determined. 

Fig. 14. Time dependent absorption of the reaction-intermediate B (trimer) observed upon UV-polymerization of TS-6 under hydrostatic pressure (a 1 bar, b 0.5 kbar, c 1.0 kbar, d 2,2 kbar). Excitation was by a single flash of excimer laser operated at 308 nm (from Ref...

P Jursinic and Govindjee (1977) Temperature dependence of delayed light emission in the 6 to 340 microsecond range after a single flash in chloroplasts. Photochem Photobiol 26 617-628... 

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