A variety of optical absorption, emission and luminescence excitation spectra have been measured in an attempt to identify the centers involved in the thermoluminescence of commercial LiF:Mg. It is concluded that the principal trapping centers consist of a hole trapped near various groupings of Mg2+ ions and vacancies. The optical absorption bands of these centers occur in the 3100–3800 Å region which contains several absorption bands corresponding to different geometries of the centers. It is suggested that the 2200-Å band arises from Mg2+ ion-vacancy complexes which have captured two holes. During thermoluminescence, holes are transported from traps to emitting centers. The luminescent center appears to be the F center both in an isolated position and when adjacent to a complex involving Mg2+ ions.
identical with those used to measure the relative changes in the Seebeck coefficient (AQ)/Q 0 . A chopper technique was used to eliminate the effect of the temperature gradient on the resistivity measurements. The relation between (AQ)/Q 0 and (Ap)/p 0 gives directly a simple function of the parameters K and JL. A second relation involving K, Q||, and Q ± is obtained from the zero-strain value of the Seebeck coefficient.We have used the K values given by Goldberg 2 to calculate (?.. and Q ± . Subtracting the electronic part of these as estimated from low-field Hall data, we have found the ratio of the components of the phonon-drag Seebeck tensor for a single Recent experimental work in this laboratory on the F-center production in synthetic sodium chloride at room temperature by ionizing radiation has revealed growth curves for synthetic crystals which differ from those obtained for halite. From Fig. 1 it can be seen that the nat-IOXI0 17 ENERGY ABSORBED (ev/cm 3 )
The degradation of photoluminescence in anthracene and in naphthalene has been studied under gamma-ray and electron irradiation over the range 3×105 to 2×108 rep. For both materials the variation of brightness with Co60 gamma-ray dose D, in rep, may be represented by (I/I0)=(1+AD)−1, where A=8.5×10−7 for anthracene and A=14×10−7 for naphthalene. Irradiation also produces a radiophotoluminescence in naphthalene, with emission in the visible spectral region. Both the degradation and radiophotoluminescence are stable with time at room temperature. The employment of these effects for dosimetry is discussed.
Two paramagnetic species have been observed in CsCl after irradiation at low temperatures with 2-Mev electrons. One of these, an anisotropic, "hole"-type center, has not yet been positively identified. The resonance signal from the other center has all the properties expected of the CsCl F center. The F-center parameters are g= 1.984±0.001, A =49.5±1.0 gauss, and the envelope width at half maximum is approximately 800 gauss. The partially resolved hyperfine lines due to the nearest-neighbor Cs nuclei have an estimated width at half maximum of 17±5 gauss. Due to the low signal-to-noise ratio only 38 of the expected 57 lines have been observed.
The presence of vacancies created by high-energy radiation in sodium chloride single crystals has been detected by comparing the F-center coloration produced by ultraviolet light after irradiation and optical bleaching to that obtained before irradiation. The behavior of the F-center. coloration as a function of time of irradiation under ultraviolet light after exposure of the crystals to high-energy radiation is different for synthetic and natural sodium chloride. This difference is attributed to the presence of hydroxyl ions in the synthetic crystals which are inadvertently introduced into the lattice during the growth of the crystals in air. The results obtained are the same whether 40-kvp x-rays, 2-Mev electrons, or Co 60 y rays are used to create the F centers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.