Temperature dependence of spin-spin and spin-lattice relaxation times of paramagnetic nitrogen defects in diamond

1998 ◽  
Vol 109 (19) ◽  
pp. 8471-8477 ◽  
Author(s):  
E. C. Reynhardt ◽  
G. L. High ◽  
J. A. van Wyk
Keyword(s):  
Temperature Dependence ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

Bonded Hydrogen and Trapped H2 in a-Si1−xGex:H Alloys

1989 ◽  
Vol 149 ◽  
Author(s):  
E. J. Vanderheiden ◽  
G. A. Williams ◽  
P. C. Taylor ◽  
F. Finger ◽  
W. Fuhs
Keyword(s):  
Temperature Dependence ◽  
Molecular Hydrogen ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
H Nmr ◽  
Local Environments

ABSTRACT1H NMR has been employed to study the local environments of bonded hydrogen and trapped molecular hydrogen (H2) in a series of a-Si1−xGex:H alloys. There is a monotonic decrease of bonded hydrogen with increasing x from ≈ 10 at. % at x = 0 (a-Si:H) to ≈ 1 at. % at x = 1 (a-Ge:H). The amplitude of the broad 1H NMR line, which is attributed to clustered bonded hydrogen, decreases continuously across the system. The amplitude of the narrow 1H NMR line, which is attributed to bonded hydrogen essentially randomly distributed in the films, decreases as x increases from 0 to ≈ 0.2. From x = 0.2 to x ≈ 0.6 the amplitude of the narrow 1H NMR line is essentially constant, and for x ≥ 0.6 the amplitude decreases once again. The existence of trapped H2 molecules is inferred indirectly by their influence on the temperature dependence of the spin-lattice relaxation times, T1. Through T1, measurements it is determined that the trapped H2 concentration drops precipitously between x = 0.1 and x = 0.2, but is fairly constant for 0.2 ≤ x ≤ 0.6. For a-Si:H (x = 0) the H2 concentration is ≈ 0.1 at. %, while for x ≥ 0.2 the concentration of H2 is ≤ 0.02 at. %.

Chlorine NQR Spin-Lattice Relaxation and Electron Spin Dynamics in Paramagnetic [Co(H2O)6[PtCl6]

1991 ◽  
Vol 46 (12) ◽  
pp. 1103-1107 ◽  
Author(s):  
Motohiro Mizuno ◽  
Tetsuo Asaji ◽  
Atsushi Tachikawa ◽  
Daiyu Nakamura
Keyword(s):  
Temperature Dependence ◽  
Electron Spin ◽  
Correlation Time ◽  
Spin Exchange ◽  
Energy Gap ◽  
Spin Dynamics ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

Abstract Chlorine NQR spin-lattice relaxation times T1Q were determined for [Co(H2O)6][PtCl6] at 4.2 400 K. Above ca. 350 K, T1Q decreased rapidly showing the onset of a reorientation of [PtCl6]2-. The activation energy Ea of this reorientation was determined as 125 ± 15 kJ mol-1. With decreasing temperature, T1Q showed a maximum at ca. 250 K. Below ca. 200 K, T1Q. is governed by the magnetic dipolar interaction between chlorines and paramagnetic Co2+ ions and is inversely proportional to the electron spin correlation time τe of CO2+ . τe is shown to be determined by the electron spin-lattice relaxation time T1e and the temperature independent correlation time rs for the spin-exchange between neighbouring ions above and below ca. 50 K, respectively. The temperature dependence of T1e is explained by assuming the Orbach process with an energy gap A/k of 530 + 20 K as T1e = 5 x 10-14 exp(530/T)s. τs was estimated to be 0.9 x 10-10 s. The temperature dependence of the ESR linewidth of Mn2+ impurities in single crystal was also measured, intending to study Co2+ spin dynamics. The limit of the ESR method is discussed by comparing the obtained results with those of the NQR method

Molecular Mobility of the Water Molecules in Aqueous Sucrose Solutions, Studied by 2H-NMR Relaxation

1994 ◽  
Vol 49 (3-4) ◽  
pp. 250-257 ◽  
Author(s):  
D. Girlich ◽  
H.-D. Lüdemann
Keyword(s):  
Temperature Dependence ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Spin Lattice ◽  
Sucrose Solutions ◽  
Deuteron Spin ◽  
High Concentrations

Deuteron spin lattice relaxation times T1 of sucrose/D2O solutions are given as function of temperature, pressure, frequency and concentration. From the temperature dependence of the 2H -T1 the rotational dynamics of the hydrated sucrose complex and the water molecules are determined. For high pressure and high concentrations the temperature dependence of the water molecules is described by a Vogel-Tammann-Fulcher equation. The ideal glass transition temperatures TOH2O derived for the water molecules are at higher concentrations almost constant and smaller than the TOsuc of the sugar molecules

Motional behavior of 2,3:5,6-di-O-isopropylidene-α-D-mannofuranose in solution. A 13C spin-lattice relaxation study

1983 ◽  
Vol 61 (7) ◽  
pp. 1542-1548 ◽  
Author(s):  
Photis Dais ◽  
Arthur S. Perlin
Keyword(s):  
Temperature Dependence ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Structural Features ◽  
Spin Lattice Relaxation ◽  
Hindered Rotation ◽  
Spin Lattice ◽  
Resonance Spin ◽  
Diffusional Model ◽  
Motional Behavior

13C nuclear magnetic resonance spin-lattice relaxation times (T1) have been used to probe the motional behavior of 2,3:5,6-di-O-isopropylidene-α-D-mannofuranose (1) in dimethyl sulfoxide solution. This system offers structural features well suited to the study of a variety of internal motions, i.e., ring oscillation, ring puckering interconversion, and methyl internal rotation, all of which are superimposed on an isotropic overall reorientation. Among various models examined to evaluate internal rotations, a two-sites jump model was found satisfactory for interpreting the oscillation and puckering motions of the flexible 5,6-O-isopropylidene ring, whereas a diffusional model described hindered rotation of the geminal methyl groups of the rigid 2,3-O-isopropylidene ring from 15° to 80 °C. The activation energy associated with the temperature dependence of the rate of overall molecular tumbling was found to agree with the hydrodynamical prediction of 4.57 kcal/mol associated with the temperature dependence of the ratio (η/T). In addition, an explicit treatment of the relaxation data vs. solution viscosities, as a function of temperature, indicated that 1 reorients under the "slip" boundary conditions.

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