RESUMEN
The thermoluminescence (TL) of calcium silicate phosphor (CSO) prepared by the sol-gel method and sintered at 1200 °C were investigated. From Tm-Tstop curve, TL emission spectrum and computer deconvolution using electron traps with discrete and continuous distributions, the glow curves were found to be composed of four TL peaks (117, 190, 250 and 275 °C) with a single emission band centered at 370 nm. Electron paramagnetic resonance (EPR) investigation has been carried out to identify the defect centers formed in the CSO phosphor by γ-irradiation and find the centers related to the TL process in the phosphor. At room temperature, three defect centers were observed. The first center, characterized by the principal g-values of 2.014, 2.011, and 2.0080 was assigned to an O- ion. The second center with g-values 2.015, 2.013, and 2.010 is also attributed to an O- ion and is associated with the TL peak at 280 °C. The third center, with an isotropic g-value of 2.0011 was identified as the F+ center (singly ionized oxygen vacancy) and relates to the TL peak at 280 °C.
RESUMEN
In this study, the thermoluminescence (TL) properties of natural NaCl from Lluta, Arequipa-Peru was investigated. The number of peaks and the kinetic parameters associated with the TL glow peaks of NaCl sample after gamma-irradiation were analyzed by initial rise and deconvolution method. Defect centers induced in pure salt by gamma irradiation have been studied by electron spin resonance (ESR) with a view to identify the centers associated with the TL process in the salt. Thermal annealing experiments indicate the presence of three defect centers. Center I characterized by the g-value 2.011 is identified as an O- ion and relates with the dominant TL peak at 220 °C. Center II with a g-value of 2.0058 is attributed to a F center and is found to correlate with the 128 °C TL peak. Center III has of g-value 2.014 and is also assigned to an O- ion.
RESUMEN
Pottery fragments from the Yumina archaeological site, Arequipa, Peru, were dated by means of thermoluminescence (TL) and optically stimulated luminescence (OSL). Electron paramagnetic resonance (EPR) technique was used to study the firing temperature using the iron signal (Fe3+) as a firing temperature reference. The ages of the samples were found to be between 1190⯱â¯30 and 1240⯱â¯80 years (777⯱â¯80 and 827⯱â¯30 A.D.) determined by both techniques. The firing temperature of ceramics was found to be around 550 ⯱ 50⯰C. Our study, based on the combination of TL and OSL techniques to study Yumina archaeological site pottery, will be helpful for archaeologists in Peru. With the results of this investigation, we can understand the chronology and determine the areas of dispersion and density of the archaeological occupation in the Arequipa Valley. In addition, the calculated ages are consistent with the occupation period of the Yumina archaeological site estimated by stratigraphic analysis of the potteries.
RESUMEN
In the present work, carbonate samples covering wall painting of four points in the same site found at Peruaçu National Park in the extreme northwest of the state of Minas Gerais, Brazil, has been investigated and dated by thermoluminescence (TL) and electron paramagnetic resonance (EPR) techniques. The EPR spectrum of the carbonate samples presented the typical six signals due to Mn2+ ion and signals around g~2.0 due to SO2- and CO2-. The thermal stability and dose response of the EPR signals were found to be suitable for an age determination using the center due to CO2-. The carbonate sample exhibits TL peaks at approximately 350⯰C. TL and EPR dating of the carbonate samples that covered the cave paintings gave an age of 33.13 to 48.40 ka. This series of dating data indicate that in the region about 220-250â¯km from the coast and extending from the State of Piaui, Bahia to Minas Gerais people lived around 50000 years ago.
RESUMEN
A cylindrical fragment of stalagmite from Caverna do Diabo, State of São Paulo, Brazil, has been studied and dated by thermoluminescence and electron paramagnetic resonance techniques. The thermoluminescence glow curves of stalagmite samples and subsequently gamma irradiated, have shown rise of three peaks at 135, 180 and 265 °C. From electron paramagnetic resonance spectra of stalagmite was possible to clearly identify three paramagnetic centers in the g = 2.0 region: Centers I, II and III are due to , and , respectively. The additive method was applied to calculate the accumulated dose using thermoluminescence peak at 265 °C and the electron paramagnetic resonance signal at g = 1.9973 of CO- 2 radical. The ages of the different slices of stalagmite were determined from the Dac- values and Dan- value, obtaining an average of 86410 for central slice, 53421 for second slice, 31490 for third slice and 46390 years B.P. for the central region of upper end.