Glow Curve Shape Research Articles

A new method of dating pottery by thermoluminescence

The shape of the thermoluminescence glow-curve of an archaeological sample depends on its archaeological age. In this work it is demonstrated that it is possible to obtain in the laboratory an artificial glow curve identical to the archaeological one. From the conditions of the laboratory experiment (temperature of irradiation and dose rate), under which the identity is achieved, it is possible to estimate the archaeological age of the sample. The theory of the method is presented and experimental results are given.

DECAY CHARACTERISTICS OF SOIL THERMOLUMINESCENCE

Thermoluminescent decay of five different types of soils (soil no. 4FF, Yolo sandy loam, Hanford sandy loam, soil no. 9RDG, and Egbert muck) irradiated by Co60 photons and in the reactor were examined. Although the glow output and the glow curve shapes differed considerably among the soils, the shape of the thermoluminescent decay curves, in general, were quite similar, whether the soil was irradiated by Co60 photons or in the reactor. Regardless of the soil type, the most rapid decay occurred within the first 24 hr after irradiation. After the lapse of sufficient decay time, an apparent isothermal equilibrium state was approached. Curves were fitted to the decay data by the use of a computer program which obtains a weighted least squares fit of a function to the data by means of stepwise Gauss-Newton iterations on the parameters. The results indicated that the thermoluminescent decay curves of soils were hyperbolic [Y = $alpha$($beta$ + X)/sup gamma/ + delta] in form. (auth)

Ultraviolet and x-ray induced recombination luminescence of L-tryptophan in low temperature polar matrices

The long-lived isothermal luminescence and thermoluminescence of L-tryptophan in 9M LiCl and in ethylene glycol/water (EG/H2O) glass irradiated with uv light and x rays have been investigated. The spectra of the luminescence as well as the effect of an electron scavenger indicate that it arises from electron-cation recombination. In EG/H2O the decay kinetics of the long-lived isothermal phosphorescence and the shape of the thermoluminescence glow curve as well as the isothermal luminescence/thermoluminescence ratio are identical for the two types of irradiation. Hence it is concluded that the distribution of electron-cation distances is the same in the two cases for the ion pairs that give rise to recombination luminescence. In LiCl/H2O glass the decay kinetics of the long-lived luminescence is the same after x-ray and uv irradiation, but the glow curves are different. This difference may be explained by the following observations: (a) x rays induce radicals and long-lived luminescence in the pure solvent; (b) in an x-irradiated LiCl/H2O glass the absorption spectra indicate that tryptophan molecules react with radicals of the solvent at about 140 K to produce tryptophan cations. Luminescence may be emitted in the reaction of these tryptophan cations with trapped electrons or anions. In EG/H2O the uv-induced recombination luminescence is pure phosphorescence of tryptophan while in LiCl/H2O fluorescence is also seen at temperatures below 130 K. This is interpreted in terms of the trapping energy of the recombining ion pairs. The fraction of the recombinations that give rise to molecules in the triplet state has been estimated from the luminescence spectra.

Study of the trapping states in ZnS single crystals grown from gallium melt

The trapping levels in zinc sulphide single crystals grown from gallium melt have been investigated using thermoluminescence techniques. The observed peak at 175° K consists of two overlapping components at 173 and 200° K respectively. Thermal activation energies and frequency factors were calculated for both traps. The dependence of glow curve shape on excitation conditions is caused by the retrapping by non-filled 200° K traps of electrons freed from 173° K traps in the course of the glow curve run. In addition to the results on “pure” crystals, measurements were made on samples grown with chlorine, oxygen and copper impurities, as well. Although no positive identification of the chemical nature of the 173 and 200° K trapping centers has been possible, we find that our results are not inconsistent with a previously suggested model in which the traps are identified as complex defects. Comparison is also made with trap spectra observed earlier in gallium-doped zinc sulphide samples prepared by the usual methods.

Use of LiF thermoluminescence plaques without furnace annealing

Describes a method requiring no furnace annealing which can be carried out with any general-purpose TLD reader with 'pre-heat' feature, a variable temperature-versus-time profile and an approximately linear heating ramp. With this method one produces LiF TLD characteristics similar to those obtained after magic annealing. The change in the shape of the LiF glow curve with changing temperature-versus-time profile is presented; reproducibility of successive dose interpretations was demonstrated; and limitations due to fading and gradual sensitivity changes is compared with those of furnace-annealed samples. Some applications of the method in medical dosimetry are discussed.

Analysis of glow curves for a material containing distributed trap levels

The theory of thermoluminescence and thermally stimulated currents is extended to the case of traps with distributed binding energies. The detailed shape of glow curves depends on the actual trap distribution. However, it seems to be possible to distinguish experimentally between discrete and distributed traps by using different doses of optical radiation to obtain different initial amounts of trapped charge, and by varying the frequency of the optical excitation to allow only certain energy levels to be occupied by excited electrons.

Thermolumineszenz von kubischem und hexagonalem ZnS/Cu / Thermoluminescence of Cubic and Hexagonal ZnS/Cu

The emission spectra, thermoluminescence glow curves and thermoluminescence spectra of cubic and hexagonal ZnS/(10-4)Cu phosphors were measured comparated to these of ZnS/ (5·10-4) Cu phosphors by excitation with light. The shape of the glow curves is correlated with the crystal structure of the materials.

Excitonic Processes and Thermoluminescence

Processes of defect creation by nonionizing radiation were studied by applying thermoluminescence methods. KBr crystals were irradiated at 80 K by monochromatic uv light in the region of 1800-2300 \AA{}. Shapes of glow curves were found to differ from those obtained after $x$ coloration. Excitation spectra of the various glow peaks as well as dose dependence of their intensities were investigated. The excitation spectrum showed maxima at the $\ensuremath{\alpha}$ band and on the long-wavelength tail of the fundamental absorption. Most of the glow peaks showed a linear dose dependence. The mechanism proposed by Pooley and by Hersh is extended to the case of defect creation by irradiation into a perturbed exciton state and excitation of thermoluminescence. An expression for the number of the defects created by the uv irradiation is derived as a function of the radiation dose. This expression takes into account the absorption coefficient of the crystal and, therefore, the penetration depth of the exciting monochromatic light. Experimental results were found to be in good agreement with those predicted by the model.

Artificially Induced Thermoluminescence of Sedimentary Dolomites

ABSTRACT Examination of gamma-ray activated glow curves of several natural dolomites revealed the presence of three groupings based on glow curve shapes. These shapes are expressed numerically as the peak height ratio of the middle temperature (235° C) peak to the low temperature (115° C) peak. If stratigraphic and petrologic evidence is acceptable for inferring the genesis of dolomites, it becomes possible to relate the three groupings to three types of sedimentary dolomites. One group of glow curves shows an intense low temperature peak relative to other peaks present and has peak height rations ranging form 0.12 to 0.45. Based on field and laboratory data, the samples represented by this group may be primary precipitates. Another group of curves has an intense middle temperature peak relative to other peaks present and has a peak hight ratio range of 1.81 to 3.53. The samples represented by this group are metasomatic dolomites. The third set of curves has low and middle temperature peaks of similar intensities and peak height rations of 0.65 to 1.30. Geologic data allow an assignment of possible penecontemporaneous (early diagenetic) origin to the dolomites of this group. Anomalies do exist using this technique for determining genesis, but whether the groupings are related to imperfections in the crystal lattice or presence of certain impurities, either of which might be unique to a particular type of dolomite, is unknown. The results are highly suggestive, and with continued research, the technique could prove valuable for supplementing other data used to determine the origin of dolomite. BRIEF HISTORY OF DOLOMITE THERMOLUMINESCENCE

Thermoluminescence Techniques in Determination of the Stress and Crystallization History of Ice

Abstract A series of glow-curve measurements were made to determine the general nature of the thermoluminescence of natural ice. The curves were made by subjecting the samples to ultraviolet radiation from a quartz-envelope mercury arc lamp while keeping the samples at liquid air temperature. The samples were then heated by passing a stream of air over the sample container. The resultant rise in temperature is non-linear but is nearly uniform from run to run. The light emitted was measured by the microphotometric portion of the standard apparatus for determination of mineral thermoluminescence. Curves were obtained on samples collected from the ice tunnel in the ice cap at Jungfraujoch and from freshly fallen and old snow at Bern in Switzerland. A systematic variation in glow-curve shape was found. This variation appears to be directly related to the stress history of the ice. Ice which has been subjected to high shearing stress can he readily distinguished from ice which has not.

Thermoluminescence Techniques in Determination of the Stress and Crystallization History of Ice

AbstractA series of glow-curve measurements were made to determine the general nature of the thermoluminescence of natural ice. The curves were made by subjecting the samples to ultraviolet radiation from a quartz-envelope mercury arc lamp while keeping the samples at liquid air temperature. The samples were then heated by passing a stream of air over the sample container. The resultant rise in temperature is non-linear but is nearly uniform from run to run. The light emitted was measured by the microphotometric portion of the standard apparatus for determination of mineral thermoluminescence.Curves were obtained on samples collected from the ice tunnel in the ice cap at Jungfraujoch and from freshly fallen and old snow at Bern in Switzerland. A systematic variation in glow-curve shape was found. This variation appears to be directly related to the stress history of the ice. Ice which has been subjected to high shearing stress can he readily distinguished from ice which has not.

Surface Correlation of Some Pennsylvanian Limestones in Mid-Continent by Thermoluminescence

Limestone samples collected from established stratigraphic horizons in outcropping Pennsylvanian rocks of Iowa, Missouri, and Kansas have been subjected to thermoluminescence study to evaluate the use of thermoluminescence in correlation. Although each limestone selected for study is a unit whose lateral continuity has been reasonably well demonstrated by other stratigraphic methods, there is wide variation among the limestones in the lateral persistence of specific thermoluminescence properties. Some show fairly persistent thermoluminescence patterns over a township-to-county area, whereas other limestones show wide variation within a square mile. Because lithologic factors, chemical composition, radioactivity, recrystallization, cyclical sedimentation, and sampling interval are capable of exerting a control upon thermoluminescence itself or influencing the interpretation of the results obtained, correlation by thermoluminescence is subject to severe limitations. Thermoluminescence curves from cyclical limestones of the Kansas City and Shawnee groups show cyclical repetitions. A relationship between glow-curve shape and lithologic character is suggested for some limestones in the cyclical sequences, but the factors controlling thermoluminescence are complex and need further study. In the limestones studied, radioactivity is either of secondary importance or its effects are masked by other factors.

Use of Thermoluminescence of Limestones in Subsurface Stratigraphy

The thermoluminescence of the limestones of the Meramecian and Chesteran series (middle and upper Mississippian) of the Illinois basin was studied in an attempt to develop the thermoluminescence of limestones into a useful research tool in subsurface geology. A powder method of sample preparation is described which makes accurate quantitative measurement of thermoluminescence possible. The apparatus used in measuring and recording thermoluminescence is described briefly. The analysis of patterns of variation in intensity of thermoluminescence and in glow-curve shapes vertically through a formation appears to have some usefulness in subsurface stratigraphy in (a) identifying and characterizing a formation, (b) assisting in recognizing tops and bottoms of limestone formations where lithologic breaks are not present, (c) splitting thick carbonate rock sequences into small units useful in correlation, and (d) recognizing erosion or non-deposition of zones by the absence of parts of the typical pattern of variation. Within certain limitations, the variations in radioactivity of the limestones appear to be the dominant factor in the cause of variations in thermoluminescence.