Thermoluminescent peak temperature

Recently, we developed a simple and discrete way to induce Ca-dependent restoration of PSII reactions in higher plant PSII. When spinach PSII membranes are treated with a low pH medium for a short period, O2 evolution is markedly inhibited by about 90% [103. Notably, this treatment removes about half of the PSII-associated Ca with no loss of extrinsic proteins, and the inactivated O2 evolution is well restored by simple addition of exogenous Ca to treated membranes. The low pH treated PSII shows an abnormal thermoluminescence band with an elevated peak temperature, indicative of modulated thermodynamical properties of the charge pair formed in the treated center [113. It was further shown that the abnormal thermoluminescence band induced by flashes does not show any oscillatory behavior on exposure to series of flashes. This has been interpreted that S2 to Sg transition is blocked in treated PSII, while Sj to S2 proceeds... 

More recently, however, we happened to observe that even in the treated membranes the EPR multiline signal can be induced, if illumination is given at higher temperatures. This finding led us to investigate the temperature dependence of to S2 transition. In this communication we report a precise comparison of the temperature dependence of to S2 transition by means of thermoluminescence and low temperature EPR spectroscopy between low pH treated and normal untreated PSII. It was found that low pH treatment not only modulates the properties of the S2 state as represented by elevated peak temperature of thermo luminescence and narrowed hyperfine line spacing of the multiline signal, but also markedly upshifts the threshold temperature of to S2 transition. 

Similar measurements of thermoluminescence glow curve and EPR spectroscopy were done at varying excitation temperatures and the amplitudes of the two signals were plotted as a function of excitation temperature to determine the half inhibition temperature of to S2 transition in low pH treated PSII. As depicted in Fig. 4A, thermoluminescence peak height of the control untreated sample (O) showed a... 

Many polymers, after irradiation at low temperature, give off light when allowed to warm. This phenomenon of thermoluminescence depends not only on the chemical structure but also on crystal morphology. In polyethylene, for example, peaks in the thermoluminescence glow curve correspond, respectively, to the crystalline and the amorphous regions (9, 19, 22) (Figure 2). 

The main argument in favour of the tunneling mechanism of the reaction was the coincidence of the kinetics observed for the ITL process at three different temperatures (4.2, 66, and 77 K) (Fig. 12). Along with the ITL, the y-irradiated solutions of Ph2 in methyl-cyclohexane display two peaks of thermoluminescence at 90 and 95 K. They were accounted for by the existence of two different recombination processes reaction of Ph2 with etr captured at long distances from Ph2+ (peak at 90 K) and reaction of Ph2+ with Ph2 (peak at 95 K) [54]. Both these processes were shown to contribute to... 

The techniques of ESR were used [10] to study radicals formed in solid state. ESR proved to be a very sensitive technique to detect radicals (10" ° mol 1 ) trapped for days, weeks and even years and discriminate between irradiated and non-irradiated drugs. Radical amounts increased linearly with absorbed doses up to 10 kGy, the radiolytic yield was constant, and ESR post-dosimetry was proposed as a new method to identify radiosterilized drugs [11]. Thermoluminescent signals are present prior to any irradiation in all the 3-lactam drugs tested [12]. The irradiated drugs showed a modification in the quality and quantity of the thermoluminescent temperature peaks. 

Radio, chemi and thermoluminescence studies on polymers continues to attract much interest as an analytical probe. The t-irradiation of pyrene and naphthalene doped polyethylene gives excimer emission in the range of the high temperature radiothermoluminescence peak whereas other workers have used the technique to establish changes in the glass transition of the polymer 40 particular feature of radiothermoluminescence is... 

This phenomenon was observed with polymers some years ago [177—183]. The more recent investigations are due to Buben and Nikolskii [183]. These workers measured the emission from many amorphous and crystalline polymers and observed correlations between the temperature corresponding to the glow peak maxima and the structural transition temperatures of the materials. A detailed study of polyethylene thermoluminescence was made by Charlesby and Partridge [184]. The glow curve obtained after irradiation in vacuo possesses three peaks, a, j3 and y, whose luminescence intensities are proportional to the irradiation dose for doses below 5 x 104 rads. The maxima occurs, respectively, at —110, —65 and —27°C, when the total... 

An Arrhenius-type plot of the probability constant p (= 0.693/tl/2) shows a break between —65 and —40°C. The activation energies of the a, 0 and y peaks are identical at temperatures below the structural transition of polyethylene. These activation energies and the related pre-exponential factors agree closely with those for molecular motion in polyethylene (Table 10). If oxygen is present during irradiation, the 3 and y glow peaks are completely removed at low doses and replaced by a new peak, e, at lower temperature. The thermoluminescence emission spectra of the a, y, e and probably the j3, glow peaks are identical and correspond to the emission of aliphatic aldehydes. 

Thermoluminescence (TL) is a widely used technique for the determination of shallow energy states in solids due to trapped electrons and holes. The basic principle is that an applied temperature will release trapped electrons when kT k = Boltzmann constant, and T = absolute temperature) is equivalent to the energy difference between the trapped state and the conduction band. Hence a type of spectrum is produced by slowly ramping the temperature of a material while its spectral emission is detected. Such a spectrum is called a glow curve, and usually plots all emitted photon intensity without discrimination of wavelength. After such a spectrum has been obtained, the full emission spectrum for every peak (i.e., temperature) in the glow curve can be obtained. In this way the ions associated with each trapping state can be identified (McKeever 1985). 

Besides radiation dosimetry, TL can be used for UV dosimetry by making use of what is termed as PTTL—Phototransfer thermoluminescence. If an irradiated material is heated past highest temperature glow peak, cooled to room temperature, and then subjected to UV light, some of the traps are refilled and TL is observed. This is termed as PTTL the intensity of emission depends upon the integrated flux of the UV photons to which the material has been exposed. Thus, from the intensity of PTTL one may back calculate the intensity of UV source. 

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