- Email: [email protected]
Compensation effect in thermoluminescence of TLD-500
Radiation Measurements 43 (2008) 259 – 262 www.elsevier.com/locate/radmeas
Compensation effect in thermoluminescence of TLD-500 I.A. Weinstein ∗ , A.S. Vokhmintsev, V.S. Kortov Ural State Technical University, 19 Mira Street, Ekaterinburg 620002, Russia
Abstract Thermoluminescence in the main dosimetric peak at 450 K in the 2.4-, 3.0- and 3.8-eV emission bands of the TLD-500 detectors has been studied. The thermoluminescent (TL) curves, which are obtained at the doses D = 10−5 .1 Gy, are approximated by the general-order kinetics equation. A compensation relation between the activation energy and the effective frequency factor is observed for all the bands. The compensation relation parameters—the isokinetic temperature Ti and the constant s0 —are estimated. Possible applications of the said quantities in practical luminescent dosimetry are noted. It is concluded that the compensation effect influences the kinetics of TL processes in the TLD-500 dosimetric crystals. © 2007 Elsevier Ltd. All rights reserved. Keywords: -Al2 O3 ; TL dosimetry; Thermally activated processes; Isokinetic temperature
1. Introduction As is known, the absorbed dose in thermoluminescent (TL) ionizing radiation detectors of the TLD-500 type, which are based on single crystals of anion-defective -Al2 O3 , is determined from the TL yield in the main dosimetric peak near 450 K (Kortov et al., 1997). This peak has an inhomogeneous spectral composition and is characterized by three basic luminescence bands at 3.0, 3.8 and 2.4 eV, which are due to defects of different origins. Today it is still topical to study luminescence temperature quenching mechanisms governing fundamental kinetic laws of TL in these bands at temperatures higher than room temperature. The earlier studies of quenching in the 3.0- and 3.8eV luminescence bands in the TLD-500 detectors revealed the compensation effect (Weinstein et al., 2006, 2007), which is reduced to a correlated change of the quenching activation energy and the pre-exponential factor. In addition, a compensation relation between the trap activation energy EA and the effective frequency factor s was deduced from the study of the dose dependence of TL at 3.8 eV in TLD-500 (Orozbek uulu Askar et al., 2006). ∗ Corresponding author. Tel.: +7 343 375 45 94; fax: +7 343 348 19 12.
E-mail address: [email protected] (I.A. Weinstein). 1350-4487/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2007.10.003
At present the compensation effect is well known in the kinetics of chemical reactions and is observed in a variety of processes having the activation component, such as the diffusion in metal and nonmetal materials, the ion transfer, the enzyme catalysis, etc. (Krysov, 2002). Some experiments are available dealing with this effect during the temperature quenching of the luminescence in organic materials (Kazakov, 1965). Observations of the compensation effect in many thermally activated processes suggest its influence on TL processes in the dosimetric crystals as well. It is well known that the parameters of TL peaks directly depend on the elements of the compensation relation, namely the trap activation energy and the corresponding frequency factors. Therefore, the objective of this study was to estimate parameters of the compensation relations by analyzing characteristics of the main dosimetric peak in different luminescence bands in the TLD-500 crystals. 2. Experimental TLD-500 samples, whose ionizing radiation sensitivity differed by not more than 10%, were chosen for the investigation. A MUM grating monochromator was used for selection of the spectral region under study during the TL measurements in the 2.4-, 3.0- and 3.8-eV bands. An optical filter with the maximum passband at 2.32 eV and FWHM = 0.25 eV was used when the
I.A. Weinstein et al. / Radiation Measurements 43 (2008) 259 – 262
TL yield in the 2.4-eV band was measured at the -radiation dose D < 60 mGy. TL was registered by a FEU-39A photomultiplier in the counting regime. The heating rate = 2 K s−1 was maintained constant during the measurements. For accumulation of the required dose of 10−5 –10 Gy, the detectors were exposed to -radiation from a 90 Sr/90 Y sources. The dose rate at the seat of the samples was 20 Gy min−1 and 30 mGy min−1 . 3. Results and discussion Fig. 1 presents the TL curves measured in the three luminescence bands for the same sample. It is seen that the 3.0-eV luminescence is dominant and makes a major informative contribution to the dosimetric response of TLD-500. The bands at 3.8 and 2.4 eV are less intense and their maximum Tm is shifted to the region of high temperatures. The 3.8- and 2.4-eV emissions in the TL spectrum are less stable in heatingirradiation cycles and, therefore, are not used as dosimetric signals for practical purposes. Nevertheless, the formation and the behavior of these bands are interesting for the research into the fundamental properties of anion-defective crystals of the aluminum oxide. The dose dependences in the three luminescence bands were measured for the samples under study. By way of example, Fig. 2 shows curves of TL in the 2.4-eV band at different irradiation doses. To estimate the parameters of the thermally activated processes under study, all the TL curves are approximated by the general-order kinetics equation (Pagonis et al., 2006): EA ITL = sn0 exp − kT b/(b−1) s T EA × 1 + (b − 1) d exp − . T0 k
(1)
Here T0 is the initial temperature, K; k is the Boltzmann constant, J K −1 ; n0 is the initial concentration of charge carriers captured on traps, m−3 ; b is the kinetics order; s is the effective frequency factor, s−1 ; and EA is the activation energy, eV. It 1500 3.0 eV 3.8 eV TL Intensity, a.u.
2.4 eV 1000
x 30
500
0 350
400
450 Temperature, K
500
550
Fig. 1. Curves of TL in the bands at 2.4, 3.0 and 3.8 eV after exposure to a dose of 0.64 Gy. For clarity, the intensities of the bands at 2.4 and 3.8 eV are magnified 30-fold.
90 2.7 mGy 5.3 mGy 8.0 mGy TL Intensity, a.u.
260
60
30
Ti = 466 K
0 350
400
450 500 Temperature, K
550
Fig. 2. Curves of TL in the 2.4-eV band. The symbols denote the experimental data; the solid lines correspond to the approximation by Eq. (1). The arrow indicates the position of the isokinetic temperature.
Table 1 TL parameters determined from Eqs. (1) and (2) Parameters
TL emission band 2.4 eV
3.0 eV
3.8 eV
(K) Tm (K) Ti (±10 K)
10−5 –1 1.0–1.2 45–55 498–485 466
10−2 –1 1.1–1.3 34–38 452–440 398 384a,b
s0 (±0.01 s−1 )
0.028
0.003
S (meV)
3.0–1.8
2.7–2.4
10−2 –1 1.2–1.5 36–45 466–450 445 394b 442c 0.020 0.072c 3.1–2.7
D (Gy)
b
a Weinstein
et al. (2006). et al. (2007). c Orozbek uulu Askar et al. (2006). b Weinstein
is seen from Fig. 2 that the experimental TL curves are highly accurately described by Eq. (1). The approximated values of the parameters are given in Table 1. A characteristic feature of the TL emission in all the bands over the interval D of the -radiation doses studied is the increase in the peak FWHM and the shift of the maximum Tm to the low-temperature region. This behavior is in agreement with the data obtained elsewhere (Kortov et al., 1997). Notice that the kinetics order increases in all the bands as the dose grows. The luminescence at 2.4 eV approaches most closely, among the others, the monomolecular process. Fig. 3 depicts the calculated values of the frequency factor versus the activation energy for all the three bands. They are well described by the compensation relation (Krysov, 2002) EA s = s0 exp , (2) kT i
I.A. Weinstein et al. / Radiation Measurements 43 (2008) 259 – 262
1015
3.0 eV 3.8 eV
1013 s, s-1
2.4 eV 11
10
Dose
109 107 0.8
1.0
1.2 EA, eV
1.4
Fig. 3. Compensation relation of TL kinetic parameters. Symbols denote the parameter values determined from the analysis of the experimental data by Eq. (1). The solid lines correspond to the approximation by relation (2).
where s0 is the constant reflecting the entropy contribution for the “traps—recombination centers” system; Ti is the isokinetic temperature corresponding to the point of constant rate of the process independently of the dose in our case. The obtained values of the parameters in Eq. (2) are given in Table 1. Notice that the results obtained for the band at 3.8 eV are in good agreement with the data reported in (Orozbek uulu Askar et al., 2006). Moreover, the isokinetic temperatures are close to Ti calculated from the analysis of the temperature quenching of the luminescence in the corresponding bands (see Table 1). Referring to Fig. 3, the energy EA decreases with growing dose. This can be explained by the fact that the energy of trapping centers are not single valued and deeper centers of one and the same type are occupied first under irradiation. In other words, the compensation relation in the thermoluminescence of TLD-500 means that the variation of the effective activation energy of the traps at different irradiation doses is compensated by the correlated change of the effective frequency factor. The frequency factor s is often interpreted as the number of interactions of a charge carrier with the lattice phonons per unit time. In the TL theory the frequency factor is related to the change of the entropy S of the system upon delocalization of a captured charge from a trap to the region of free charge carriers (Chen and McKeever, 1997) as S s ∼ exp . (3) k The comparison of expressions (2) and (3) shows that S = EA /Ti . Table 1 contains calculated values of the entropy variation upon an elementary event of the thermal activation during TL after -irradiation. Notice that the increments S have similar values and decrease with growing dose in all the bands studied. According to Orozbek uulu Askar et al. (2006), the isokinetic temperature Ti for TL at 3.8 eV corresponds to the position of the maximum Tm at the doses (D > 4 Gy) when the TL response of the TLD-500 detectors flattens out. In the present study this fact is also confirmed for TL in the 2.4-eV band. The peak, which was measured after the exposure to the dose D = 9.6 Gy, has the maximum Tm = 467 K coinciding with Ti
261
(see Table 1). Thus, the compensation relation can be used to estimate the displacement intervals of the temperature of the dosimetric peaks depending on the dose load. Values of Ti can be also useful for substantiation of methods applied to read the dosimetric information during OSL measurements. Measurements at these temperatures should guarantee one and the same rate of all the kinetic processes independently of the “history” and the state of the detector and, hence, should improve the reliability of the absorbed dose estimation. In closing we shall note that the compensation relation is characteristic of the kinetics of the reactions involving structural units of a single “homologous” series. For example, central metal atoms capable of coordinating a series of different ligands serve as the homologous basis of complexation reactions in inorganic systems (Kazakov, 1968). The “homology core” of the thermoluminescence is most likely the traps of some origin responsible for the corresponding emission band. 4. Conclusion Thus, the kinetics of the main TL peak at 450 K in the TLD500 detectors was studied in the luminescence bands at 3.0, 3.8 and 2.4 eV at the doses corresponding to the linear and superlinear dosimetric responses. It was shown that the obtained glow curves are well described by the general-order kinetics equation. The kinetic parameters of the corresponding TL processes were calculated. The compensation effect was observed in all the bands: the decrease in the activation energy EA with growing dose was compensated by the correlated decrease in the frequency factor s. The obtained values of the compensation parameters s0 and Ti are in agreement with the results obtained elsewhere. It was shown that from the fundamental viewpoint the compensation relation (2) takes into account the effect of the entropy factor on the thermally activated components of the TL processes. The entropy increment was evaluated for the “traps—recombination centers” system in the detectors under study. The performed analysis suggests that the change of the kinetics of the TL processes in the main dosimetric peak of the TLD-500 crystals can be viewed as the direct consequence of the compensation relation between the activation energy and the frequency factor of the traps responsible for the observed thermoluminescence. Possible applications of the estimated isokinetic temperature Ti in the practical luminescence dosimetry were noted. References Chen, R., McKeever, S.W.S., 1997. Theory of Thermoluminescence and Related Phenomena. World Scientific, Singapore. Kazakov, V.P., 1965. On temperature quenching of luminescence Compensation effect. Opt. Spektrosk XVIII, 54–57. Kazakov, V.P., 1968. Compensation effect in reaction kinetics of complex ions of transition elements. Izv. SO AN SSSR, ser. “Chemistry” 7 (3), 102–112. Kortov, V.S., Milman, I.I., Nikiforov, S.V., 1997. Specific features in the kinetics of thermally stimulated luminescence of -Al2 O3 crystals containing defects. Phys. Solid State 39 (9), 1369–1373.
262
I.A. Weinstein et al. / Radiation Measurements 43 (2008) 259 – 262
Krysov, V.I., 2002. Compensation effects of the kinetics of thermoactivated processes in amorphous metallic alloys. Phys. Met. Metallogr. 93 (3), 257–261. Orozbek uulu Askar, Weinstein, I.A., Slesarev, A.I., Kortov, V.S., 2006. Kinetic features of thermoluminescence in oxygen-deficient crystals of aluminum oxide. Russ. Phys. J. 10 (Suppl.), 138–141. Pagonis, V., Kitis, G., Furetta, C., 2006. Numerical and Practical Exercises in Thermoluminescence. Springer, New York.
Weinstein, I.A., Vohmintsev, A.S., Kortov, V.S., 2006. Thermal quenching of 3.0-eV photoluminescence in -Al2 O3 single crystals. Tech. Phys. Lett. 32 (1), 58–60. Weinstein, I.A., Kortov, V.S., Vohmintsev, A.S., 2007. The compensation effect during luminescence of anion centers in aluminum oxide. J. Lumin. 122–123, 342–344.
Compensation effect in thermoluminescence of TLD-500 I.A. Weinstein ∗ , A.S. Vokhmintsev, V.S. Kortov Ural State Technical University, 19 Mira Street, Ekaterinburg 620002, Russia
Abstract Thermoluminescence in the main dosimetric peak at 450 K in the 2.4-, 3.0- and 3.8-eV emission bands of the TLD-500 detectors has been studied. The thermoluminescent (TL) curves, which are obtained at the doses D = 10−5 .1 Gy, are approximated by the general-order kinetics equation. A compensation relation between the activation energy and the effective frequency factor is observed for all the bands. The compensation relation parameters—the isokinetic temperature Ti and the constant s0 —are estimated. Possible applications of the said quantities in practical luminescent dosimetry are noted. It is concluded that the compensation effect influences the kinetics of TL processes in the TLD-500 dosimetric crystals. © 2007 Elsevier Ltd. All rights reserved. Keywords: -Al2 O3 ; TL dosimetry; Thermally activated processes; Isokinetic temperature
1. Introduction As is known, the absorbed dose in thermoluminescent (TL) ionizing radiation detectors of the TLD-500 type, which are based on single crystals of anion-defective -Al2 O3 , is determined from the TL yield in the main dosimetric peak near 450 K (Kortov et al., 1997). This peak has an inhomogeneous spectral composition and is characterized by three basic luminescence bands at 3.0, 3.8 and 2.4 eV, which are due to defects of different origins. Today it is still topical to study luminescence temperature quenching mechanisms governing fundamental kinetic laws of TL in these bands at temperatures higher than room temperature. The earlier studies of quenching in the 3.0- and 3.8eV luminescence bands in the TLD-500 detectors revealed the compensation effect (Weinstein et al., 2006, 2007), which is reduced to a correlated change of the quenching activation energy and the pre-exponential factor. In addition, a compensation relation between the trap activation energy EA and the effective frequency factor s was deduced from the study of the dose dependence of TL at 3.8 eV in TLD-500 (Orozbek uulu Askar et al., 2006). ∗ Corresponding author. Tel.: +7 343 375 45 94; fax: +7 343 348 19 12.
E-mail address: [email protected] (I.A. Weinstein). 1350-4487/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2007.10.003
At present the compensation effect is well known in the kinetics of chemical reactions and is observed in a variety of processes having the activation component, such as the diffusion in metal and nonmetal materials, the ion transfer, the enzyme catalysis, etc. (Krysov, 2002). Some experiments are available dealing with this effect during the temperature quenching of the luminescence in organic materials (Kazakov, 1965). Observations of the compensation effect in many thermally activated processes suggest its influence on TL processes in the dosimetric crystals as well. It is well known that the parameters of TL peaks directly depend on the elements of the compensation relation, namely the trap activation energy and the corresponding frequency factors. Therefore, the objective of this study was to estimate parameters of the compensation relations by analyzing characteristics of the main dosimetric peak in different luminescence bands in the TLD-500 crystals. 2. Experimental TLD-500 samples, whose ionizing radiation sensitivity differed by not more than 10%, were chosen for the investigation. A MUM grating monochromator was used for selection of the spectral region under study during the TL measurements in the 2.4-, 3.0- and 3.8-eV bands. An optical filter with the maximum passband at 2.32 eV and FWHM = 0.25 eV was used when the
I.A. Weinstein et al. / Radiation Measurements 43 (2008) 259 – 262
TL yield in the 2.4-eV band was measured at the -radiation dose D < 60 mGy. TL was registered by a FEU-39A photomultiplier in the counting regime. The heating rate = 2 K s−1 was maintained constant during the measurements. For accumulation of the required dose of 10−5 –10 Gy, the detectors were exposed to -radiation from a 90 Sr/90 Y sources. The dose rate at the seat of the samples was 20 Gy min−1 and 30 mGy min−1 . 3. Results and discussion Fig. 1 presents the TL curves measured in the three luminescence bands for the same sample. It is seen that the 3.0-eV luminescence is dominant and makes a major informative contribution to the dosimetric response of TLD-500. The bands at 3.8 and 2.4 eV are less intense and their maximum Tm is shifted to the region of high temperatures. The 3.8- and 2.4-eV emissions in the TL spectrum are less stable in heatingirradiation cycles and, therefore, are not used as dosimetric signals for practical purposes. Nevertheless, the formation and the behavior of these bands are interesting for the research into the fundamental properties of anion-defective crystals of the aluminum oxide. The dose dependences in the three luminescence bands were measured for the samples under study. By way of example, Fig. 2 shows curves of TL in the 2.4-eV band at different irradiation doses. To estimate the parameters of the thermally activated processes under study, all the TL curves are approximated by the general-order kinetics equation (Pagonis et al., 2006): EA ITL = sn0 exp − kT b/(b−1) s T EA × 1 + (b − 1) d exp − . T0 k
(1)
Here T0 is the initial temperature, K; k is the Boltzmann constant, J K −1 ; n0 is the initial concentration of charge carriers captured on traps, m−3 ; b is the kinetics order; s is the effective frequency factor, s−1 ; and EA is the activation energy, eV. It 1500 3.0 eV 3.8 eV TL Intensity, a.u.
2.4 eV 1000
x 30
500
0 350
400
450 Temperature, K
500
550
Fig. 1. Curves of TL in the bands at 2.4, 3.0 and 3.8 eV after exposure to a dose of 0.64 Gy. For clarity, the intensities of the bands at 2.4 and 3.8 eV are magnified 30-fold.
90 2.7 mGy 5.3 mGy 8.0 mGy TL Intensity, a.u.
260
60
30
Ti = 466 K
0 350
400
450 500 Temperature, K
550
Fig. 2. Curves of TL in the 2.4-eV band. The symbols denote the experimental data; the solid lines correspond to the approximation by Eq. (1). The arrow indicates the position of the isokinetic temperature.
Table 1 TL parameters determined from Eqs. (1) and (2) Parameters
TL emission band 2.4 eV
3.0 eV
3.8 eV
(K) Tm (K) Ti (±10 K)
10−5 –1 1.0–1.2 45–55 498–485 466
10−2 –1 1.1–1.3 34–38 452–440 398 384a,b
s0 (±0.01 s−1 )
0.028
0.003
S (meV)
3.0–1.8
2.7–2.4
10−2 –1 1.2–1.5 36–45 466–450 445 394b 442c 0.020 0.072c 3.1–2.7
D (Gy)
b
a Weinstein
et al. (2006). et al. (2007). c Orozbek uulu Askar et al. (2006). b Weinstein
is seen from Fig. 2 that the experimental TL curves are highly accurately described by Eq. (1). The approximated values of the parameters are given in Table 1. A characteristic feature of the TL emission in all the bands over the interval D of the -radiation doses studied is the increase in the peak FWHM and the shift of the maximum Tm to the low-temperature region. This behavior is in agreement with the data obtained elsewhere (Kortov et al., 1997). Notice that the kinetics order increases in all the bands as the dose grows. The luminescence at 2.4 eV approaches most closely, among the others, the monomolecular process. Fig. 3 depicts the calculated values of the frequency factor versus the activation energy for all the three bands. They are well described by the compensation relation (Krysov, 2002) EA s = s0 exp , (2) kT i
I.A. Weinstein et al. / Radiation Measurements 43 (2008) 259 – 262
1015
3.0 eV 3.8 eV
1013 s, s-1
2.4 eV 11
10
Dose
109 107 0.8
1.0
1.2 EA, eV
1.4
Fig. 3. Compensation relation of TL kinetic parameters. Symbols denote the parameter values determined from the analysis of the experimental data by Eq. (1). The solid lines correspond to the approximation by relation (2).
where s0 is the constant reflecting the entropy contribution for the “traps—recombination centers” system; Ti is the isokinetic temperature corresponding to the point of constant rate of the process independently of the dose in our case. The obtained values of the parameters in Eq. (2) are given in Table 1. Notice that the results obtained for the band at 3.8 eV are in good agreement with the data reported in (Orozbek uulu Askar et al., 2006). Moreover, the isokinetic temperatures are close to Ti calculated from the analysis of the temperature quenching of the luminescence in the corresponding bands (see Table 1). Referring to Fig. 3, the energy EA decreases with growing dose. This can be explained by the fact that the energy of trapping centers are not single valued and deeper centers of one and the same type are occupied first under irradiation. In other words, the compensation relation in the thermoluminescence of TLD-500 means that the variation of the effective activation energy of the traps at different irradiation doses is compensated by the correlated change of the effective frequency factor. The frequency factor s is often interpreted as the number of interactions of a charge carrier with the lattice phonons per unit time. In the TL theory the frequency factor is related to the change of the entropy S of the system upon delocalization of a captured charge from a trap to the region of free charge carriers (Chen and McKeever, 1997) as S s ∼ exp . (3) k The comparison of expressions (2) and (3) shows that S = EA /Ti . Table 1 contains calculated values of the entropy variation upon an elementary event of the thermal activation during TL after -irradiation. Notice that the increments S have similar values and decrease with growing dose in all the bands studied. According to Orozbek uulu Askar et al. (2006), the isokinetic temperature Ti for TL at 3.8 eV corresponds to the position of the maximum Tm at the doses (D > 4 Gy) when the TL response of the TLD-500 detectors flattens out. In the present study this fact is also confirmed for TL in the 2.4-eV band. The peak, which was measured after the exposure to the dose D = 9.6 Gy, has the maximum Tm = 467 K coinciding with Ti
261
(see Table 1). Thus, the compensation relation can be used to estimate the displacement intervals of the temperature of the dosimetric peaks depending on the dose load. Values of Ti can be also useful for substantiation of methods applied to read the dosimetric information during OSL measurements. Measurements at these temperatures should guarantee one and the same rate of all the kinetic processes independently of the “history” and the state of the detector and, hence, should improve the reliability of the absorbed dose estimation. In closing we shall note that the compensation relation is characteristic of the kinetics of the reactions involving structural units of a single “homologous” series. For example, central metal atoms capable of coordinating a series of different ligands serve as the homologous basis of complexation reactions in inorganic systems (Kazakov, 1968). The “homology core” of the thermoluminescence is most likely the traps of some origin responsible for the corresponding emission band. 4. Conclusion Thus, the kinetics of the main TL peak at 450 K in the TLD500 detectors was studied in the luminescence bands at 3.0, 3.8 and 2.4 eV at the doses corresponding to the linear and superlinear dosimetric responses. It was shown that the obtained glow curves are well described by the general-order kinetics equation. The kinetic parameters of the corresponding TL processes were calculated. The compensation effect was observed in all the bands: the decrease in the activation energy EA with growing dose was compensated by the correlated decrease in the frequency factor s. The obtained values of the compensation parameters s0 and Ti are in agreement with the results obtained elsewhere. It was shown that from the fundamental viewpoint the compensation relation (2) takes into account the effect of the entropy factor on the thermally activated components of the TL processes. The entropy increment was evaluated for the “traps—recombination centers” system in the detectors under study. The performed analysis suggests that the change of the kinetics of the TL processes in the main dosimetric peak of the TLD-500 crystals can be viewed as the direct consequence of the compensation relation between the activation energy and the frequency factor of the traps responsible for the observed thermoluminescence. Possible applications of the estimated isokinetic temperature Ti in the practical luminescence dosimetry were noted. References Chen, R., McKeever, S.W.S., 1997. Theory of Thermoluminescence and Related Phenomena. World Scientific, Singapore. Kazakov, V.P., 1965. On temperature quenching of luminescence Compensation effect. Opt. Spektrosk XVIII, 54–57. Kazakov, V.P., 1968. Compensation effect in reaction kinetics of complex ions of transition elements. Izv. SO AN SSSR, ser. “Chemistry” 7 (3), 102–112. Kortov, V.S., Milman, I.I., Nikiforov, S.V., 1997. Specific features in the kinetics of thermally stimulated luminescence of -Al2 O3 crystals containing defects. Phys. Solid State 39 (9), 1369–1373.
262
I.A. Weinstein et al. / Radiation Measurements 43 (2008) 259 – 262
Krysov, V.I., 2002. Compensation effects of the kinetics of thermoactivated processes in amorphous metallic alloys. Phys. Met. Metallogr. 93 (3), 257–261. Orozbek uulu Askar, Weinstein, I.A., Slesarev, A.I., Kortov, V.S., 2006. Kinetic features of thermoluminescence in oxygen-deficient crystals of aluminum oxide. Russ. Phys. J. 10 (Suppl.), 138–141. Pagonis, V., Kitis, G., Furetta, C., 2006. Numerical and Practical Exercises in Thermoluminescence. Springer, New York.
Weinstein, I.A., Vohmintsev, A.S., Kortov, V.S., 2006. Thermal quenching of 3.0-eV photoluminescence in -Al2 O3 single crystals. Tech. Phys. Lett. 32 (1), 58–60. Weinstein, I.A., Kortov, V.S., Vohmintsev, A.S., 2007. The compensation effect during luminescence of anion centers in aluminum oxide. J. Lumin. 122–123, 342–344.