eV For Peak Research Articles

Normal and anomalous heating rate effects on thermoluminescence of Ce-doped ZnB2O4

The effect of heating rate (HR) on thermoluminescence (TL) glow curves of 1%, 4%, and 10% Ce3 + doped ZnB2O4 phosphors was investigated in detail. The glow peaks are examined and, activation energy (E) and frequency factor (s) are determined by using various heating rate (VHR) method. In the obtained glow curves with nine different HRs between 2 and 10°C/s, it was observed that the TL intensities of the first peaks of all three samples and the second peak of 10% Ce3 + doped sample decrease with increasing HR. The decrease in TL intensity was investigated whether it may be due to the presence of thermal quenching or not. On the other hand, the second glow peaks of 1, 4% Ce3 + doped ZnB2O4 phosphors show an anomalous TL behavior, which the probability of the radiative processes increases due to recombination of free electrons, so the TL intensity increases with the HR. The graphs of full width at the half maximum (FWHM) versus HR were also plotted to evaluate the influence of HR on TL intensity. In this paper, we suggest that the non-localized Schön – Klasens model may give an explanation for the second peaks of 1, 4% Ce3 + doped ZnB2O4 phosphors showing an unexpected increase with the increasing HR. In addition, the calculated E values of all doped phosphors were found similar in the range of 0.47–0.53eV for peak 1 and 0.61–0.66eV for peak 2. However, s values of Ce3 + doped ZnB2O4 phosphors were found slightly different according to the dopant amount and the equation used. Furthermore, different amount of Ce3 + doped samples indicate the similar properties for the repeated cycles of 5Gy in the same irradiation conditions.

Thermoluminescence of kunzite: A study of kinetic processes and dosimetry characteristics

Since the use of natural minerals for dating and dose reconstruction using luminescence techniques is well-established and always of interest, we present thermoluminescence characteristics of kunzite, a gem variety of spodumene. The chemical composition of the sample was determined using an Electron Probe MicroAnalyzer to be (Li0.996Na0.009Mn0.006)∑=1.016(Al0.981Cr0.003Fe2+0.001)∑=0.995[(Si1.993Al0.008)∑=2.000O6].Thermoluminescence glow curves measured at 0.5K/s after laboratory irradiation consist of three prominent peaks at 338K (labelled as peak I), 454K (peak II) and 681K (peak III). The dose response of these three peaks is linear in the range 20–308Gy studied. The position of each of the peaks is independent of dose, an archetypical feature of first order behaviour. However, detailed kinetic analyses showed that in fact, the peaks are not subject to first order kinetics. Each of the three peaks is affected by thermal quenching with an associated activation energy of thermal quenching estimated to be 0.70, 1.35 and 0.54eV for peaks I, II and III respectively. In terms of dosimetry use, only peak III was found to be reliable for possible use in luminescence dating and dose reconstruction.

Investigating the plasma parameters of an Ar/O2 discharge during the sputtering of Al targets in an inverted cylindrical magnetron

The plasma parameters and reaction kinetics in an inverted cylindrical magnetron chamber have been studied with an energy resolved mass spectrometer during the sputtering of aluminum targets in an Ar/O2 discharge. Mixtures of argon and oxygen were studied as a function of oxygen percentage (0%–90%) in the discharge. The plasma was powered at 4 kW and 40 kHz at a process pressure of 5 mTorr. Al+, Al, AlO, AlO+, O2+, O+, Al2O+, and Ar+ were among the species detected in the discharge. The deposition rate of the deposited thin film decreased with increasing oxygen percentage in the discharge and results indicated that the pure gamma-alumina was obtained when the percentage of oxygen was approximately 70%. The linear plot of energy distributions of the positively charged film forming species changed from a single peak to a bimodal distribution as the percentage of oxygen exceeds 65%. In a log plot, however, the distributions showed multiple peaks ranging from 2 eV to 78 eV. Fluctuations of about 1 eV in peak energies were observed.

Analysis of the thermoluminescence from pure calcium sulphide single crystals, 8 to 300 K

Thermoluminescence is measured from pure single crystals of calcium sulphide over the temperature range 8 to 300 K. The density of data gathered allows a range of analysis techniques to be applied. Four major peaks are found and analysis gives the thermal excitation energies as 0.25, 0.36 to 0.38, 0.73 and 0.68 eV for peaks near 108, 156, 228 and 261 K, respectively.

Thermoluminescence studies on photosynthetic energy conversion. II. Activation energies for three energy storage states associated with Photoreaction II of higher plants

Thermoluminescent glow curves of isolated chloroplasts were analyzed to determine activation energy, frequency factor and lifetime of the three glow peaks associated with Photoreaction II. Peak 1 had an activation energy of 0.8 eV, a frequency factor of 1.5 · 10 14/s and a lifetime of 0.02 s. This glow peak appeared to be rather different from peaks 2 and 3, which were quite similar to each other. Peaks 2 and 3 gave activation energies respectively of 0.48 eV and 0.57 eV, frequency factors of 7 · 10 7/s and 1 · 10 9/s, and lifetimes of about 1.5 s. A second, less reliable method of analysis gave activation energies of 0.72 eV for peak 1 and 0.44 eV for peak 2. Our values are compared with those obtained by other workers, and the possible metastable states reflected by the three glow peaks are discussed.