Decay curves, analyzed with pulsed

Figure 160 Voltage (a) and current (b) dependence of the time-resolved EL in tetracene single crystals, (a) Reading from bottom to top are the bias voltage Uo, the rectangular voltage pulses (U— U0), the relaxation curves of electroluminescence (F) referring to the steady-stale EL level F0, the analyzing voltage pulses with varying duration time to and delay time t(. (b) The EL decay for two different thickness (d) tetracene crystals (crystal I d 16.5 pm pm crystal II d = 118 pm) under different steady-state current conditions (1 j 63 pA/cirr 2 j 23 pA/cm2 3 j = 0.7 pA/cm2 4 / 28 pA/cirr 5 6.1 pA/cm2). Adapted from Ref. [415],...

The voltage pulse produced by the TAC is fed to the multichannel analyzer (MCA), and is stored in a specific channel according to its amplitude, and hence time, post-excitation. The probability of a single photon event being counted is high soon after excitation and decreases with time. Repetitive operation of the TAC produces a probability histogram for the detection of fluorescence photons, which is identical to the fluorescence decay curve. 

Typical decay curves of benzophenone (BP) phosphorescence (analyzed at 450 nm) at various temperatures in PMMA excited by a 10-ns nitrogen laser pulse at 337 nm are shown in Fig. 1 (6). The phosphorescence intensity, l(t), decreases as a single exponential below the temperature corresponding to the ester side-group rotation (Tq = -3O C for PMMA). Deviations from a single-exponential decay are observed for T>Tg, which increase with increasing temperature, but the deviation becomes less marked above the glass transition temperature, T, of the matrix polymer and disappears at 15O C. 

Evidently, fluorescers with decay times much longer than the lamp pulse characteristics can be analyzed in much the same way as radioactive decay curves. A semilogarithmic plot of fluorescence intensity against time is linear, with a slope proportional to the decay time and the ordinate intercept providing a quantitative measure of the amount of fhiorophore. If the lamp pulse time and the decay time of the fhiorophore are comparable, the fluorophore s decay charac-... 

This type of research uses pulsed and tunable la.sers as an excitation source. The rare earth ion is excited selectively with a laser pulse,and its decay is analyzed. The shape of the decay curve is characteristic of the physical processes in the compound under study. For a detailed review the reader is referred to the literature [1-3]. Here we give some results for specific situations. We assume that the object of our study consists of a compound of a rare earth ion S which contains also some ions A which are able to trap the migrating excitation energy of S by SA transfer. 

Fig. 8. An example of picosecond-time-region decay of photoabsorption (620 nm) of trapped electrons in Degussa (Evonic) P25 particles after excitation by a ca. 100-fs pump pulse (310 nm). The curve was analyzed by a second-order rate law (Eq. (4)) with a baseline component (BL), and a second-order rate constant ( r) was obtained to be 13 cm ps. ...

The decay of fluorine atoms in the other reactions was estimated to be less than 1%.229,241 Pulse radiolysis combined with UV absorption was employed by Jodkowski et al.229 at pressures of 500 - 1000 mbar (M = SF6), while a fast-flow system with a quadruple mass spectrometer was applied at pressures in the range of 0.7 - 5.1 mbar (M = He). The influence of other homogeneous reactions on the reaction kinetics was also analyzed by computer simulation and found to be negligible. The rate constant ki = (1.3 + 0.3) x 10 10 cm3molecule"1s 1 at 298 K has been estimated at pressures of 500 - 1000 mbar of SF5.229 The theoretical analysis of the reaction kinetics was based on the approach developed by Troe et al.17 23 The fall-off curves for the reaction CH3... 

Figure 5. Time-resolved fluorescence of pyranine at the wavelength of maximum

The theory of bubble nucleation in a superheated liquid was first applied to the concept of thermal inkjet by Allen et al. [7]. They were able to determine the minimum cmiditions for the first bubble nucleation by applying Hsu s theory [10]. Time dependent temperature profiles above a heater surface were obtained. By superimposing the activation curve with the thermal boimdary layer, the initial bubble size and the minimum temperature for nucleation were determined. Based on a one-dimensional model and by assuming the nucleation temperature to be the superheat limit of the liquid at 330°C transient temperature profiles for the heater structure and the bubble surface after nucleation were obtained. It was noticed that the decay time to ambient temperature from its initial state was only several microseconds after 6 ps heating pulse. The thermal effects of the passivation (protective coating) layer on the heater surface were also analyzed. The results showed that the effective pulse energy required for bubble nucleation increases with the thickness of the passivation layer. 

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