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Pressure dependence of F-center hyperfine interactions
Solid State Communications,
Vol. 10, pp.v—xi, 1972.
Pergamon Press.
Printed in Great Britain
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids ‘J Phys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article. 1.
PRESSURE DEPENDENCE OF FCENTER HYPERFINE INTERACTIONS
approximately 10% of the Fe can easily be detected. A third Fe signal not previously
A.B. Woibarst, Department of Physics, Dartmouth College, Hanover, New Hampshire, U.S.A.
characterized was also noted. Because of a strong analogy with recent work on the similar compound 3~ ions on Ti0 2, the centers identified with as Fe substitutional sitesare associated a nearby defect. The charge compensation problem of a 3— ion in the host is the reason for expecting the associated defect.
We report a study of the effects of intense hydrostatic stress (10k bars) on the ENDOR spectra of F-centers in several alkali halides. in LiF, KC1, and KBr, the first shell contact hyperfine interaction constant, a 1, increases with cornpression, while the second shell term, a11, decreases. In LiCl, however, dajj/dP and daj/dP are both less than zero. We explain our experimental results, including the anomaly of LiCl, with a model involving (1) ionic motion in a nonconstant spin—density gradient and (2) ion-motioninduced perturbation of the F-center envelope function.
Recei~ed4 .‘ilav 1971 Revised 20 ~1arch 1972
3.
Received 28 Sepi ember 1971
2.
PROTON TRANSFER CONDUCTION IN AMMONIUM PERCHLORATE P.W.M. Jacobs and Wee Lam Ng. Department of Chemistry, University of Western Ontario, London 72, Ontario, Canada
The electrical conductivity both of compressed pellets and of single crystals of ammonium perchlorate has been measured from room temperature up to decomposition temperatures. Special attention has been paid to the effects of thermal cycling experiments up to various maximum temperatures. These experiments disclose that, except in very carefully annealed samples, the low temperature region (K 127°C)is structure sensitive. The low temperature conductivity is increased by several orders of magnitude by either thermal decomposition, or the adsorption of water or of ammonia. The kinetics of annealing, and of sorption and desorption of ammonia, have been studied; they differ for pellets and single crystals and show that in pellets surface adsorption is the most
ELECTRON PARAMAGNETIC RESONANCE OF A NEW Fe~ CENTER IN Sn02 R.R. Bartkowski and J.A. Tunheim, Sandia Laboratories, Albuquerque. New Mexico 87115.
The EPR spectrum of single crystal, Ni doped, Stannic Oxide, Sn02, has been reexamined at 22.7GHz. The signal which appeared after NI doping appears to be due to a new Fe~ center. Since the As grown samples contained approximately 30 ppm Fe and a strong Fe~ substitutional resonance was observed, a signal due to
important phenomenon but in single crystals V
Vol. 10, pp.v—xi, 1972.
Pergamon Press.
Printed in Great Britain
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids ‘J Phys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article. 1.
PRESSURE DEPENDENCE OF FCENTER HYPERFINE INTERACTIONS
approximately 10% of the Fe can easily be detected. A third Fe signal not previously
A.B. Woibarst, Department of Physics, Dartmouth College, Hanover, New Hampshire, U.S.A.
characterized was also noted. Because of a strong analogy with recent work on the similar compound 3~ ions on Ti0 2, the centers identified with as Fe substitutional sitesare associated a nearby defect. The charge compensation problem of a 3— ion in the host is the reason for expecting the associated defect.
We report a study of the effects of intense hydrostatic stress (10k bars) on the ENDOR spectra of F-centers in several alkali halides. in LiF, KC1, and KBr, the first shell contact hyperfine interaction constant, a 1, increases with cornpression, while the second shell term, a11, decreases. In LiCl, however, dajj/dP and daj/dP are both less than zero. We explain our experimental results, including the anomaly of LiCl, with a model involving (1) ionic motion in a nonconstant spin—density gradient and (2) ion-motioninduced perturbation of the F-center envelope function.
Recei~ed4 .‘ilav 1971 Revised 20 ~1arch 1972
3.
Received 28 Sepi ember 1971
2.
PROTON TRANSFER CONDUCTION IN AMMONIUM PERCHLORATE P.W.M. Jacobs and Wee Lam Ng. Department of Chemistry, University of Western Ontario, London 72, Ontario, Canada
The electrical conductivity both of compressed pellets and of single crystals of ammonium perchlorate has been measured from room temperature up to decomposition temperatures. Special attention has been paid to the effects of thermal cycling experiments up to various maximum temperatures. These experiments disclose that, except in very carefully annealed samples, the low temperature region (K 127°C)is structure sensitive. The low temperature conductivity is increased by several orders of magnitude by either thermal decomposition, or the adsorption of water or of ammonia. The kinetics of annealing, and of sorption and desorption of ammonia, have been studied; they differ for pellets and single crystals and show that in pellets surface adsorption is the most
ELECTRON PARAMAGNETIC RESONANCE OF A NEW Fe~ CENTER IN Sn02 R.R. Bartkowski and J.A. Tunheim, Sandia Laboratories, Albuquerque. New Mexico 87115.
The EPR spectrum of single crystal, Ni doped, Stannic Oxide, Sn02, has been reexamined at 22.7GHz. The signal which appeared after NI doping appears to be due to a new Fe~ center. Since the As grown samples contained approximately 30 ppm Fe and a strong Fe~ substitutional resonance was observed, a signal due to
important phenomenon but in single crystals V