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LOW-TEMPERATURE PARAMAGNETIC RELAXATION OF COLOR CENTERS IN KCI

Journal Article · · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D
;
The spin-lattice relaxation of color centers in KCl was experimentally studied at liquid helium temperatures by following the recovery of the magnetization affter saturation of the electron spin resonance. X-irradiated and additively colored crystals were studied and found to behave in the same manner. For crystals containing only F centers, the recovery rates were roughly proportional to the F-center concentration. A tendency toward coacentration independence at the lower concentrations was observed. The most dilute system studied had about 8 x 10/sup 16/ F centers/cc, and showed a relaxation rate at 2 deg K of 2.2 x 10/sup -3/ sec/sup -1/. Measurements at 1.4 deg K indicated a linear temperature dependence for the relaxation rate. A crystal containing 3 x l0/sup 18/ F centers/cc showed an initial recovery rate of about 0.1 sec/sup -1/. The recovery was non-exponential, and the terminal recovery rate was about 0.03 sec/sup -1/. Measurements at the same temperatures as those used for the dilute system showed the relaxation rate to be temperature independent. Samples of lntermediate concentration gave a smooth transition between these two types of behavior. Measurements in magnetic fields of 3500 and 1750 gauss indicate a fieldindependent relaxation rate for all samples. After optical bleaching in the F absorption band, with concomitant production of M, R, and N centers, crystals showed an increased recovery rate for both the initial and terminal portrons of the recovery. As bleaching progressed, the recovery became more nonexponential and less temperature dependent. Increases in relaxation rates by factors of several hundred were observed with no signs of saturation of the effect. Subsequent thermal bleaching of M, R, and N centers restored the relaxation rate to its value prior to optical bleaching. Details of sample preparation are given, as is a discussion of possible explanations of the results. (auth)
Research Organization:
Cornell Univ., Ithaca, N.Y.
NSA Number:
NSA-16-025985
OSTI ID:
4825835
Journal Information:
Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 126; ISSN PHRVA
Country of Publication:
Country unknown/Code not available
Language:
English

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Related Subjects

COLOR CENTERS
DIFFUSION LENGTH
ELECTROLYTES
EQUATIONS
HELIUM
LATTICES
LIQUIDS
LOW TEMPERATURE
MAGNETIC FIELDS
MAGNETISM
MASERS
MEASURED VALUES
OSCILLATIONS
OSCILLATORS
PARAMAGNETISM
PHYSICS
PLASMA
POTASSIUM CHLORIDES
RELAXATION
RESONANCE
SLOWDOWN
SPIN
TRANSIENTS
VACANCIES