scholarly journals Reorientation of thiophene molecules in a benzene lattice

1978 ◽  
Vol 56 (5) ◽  
pp. 714-716 ◽  
Author(s):  
William E. Sanford ◽  
Robert K. Boyd ◽  
John A. Ripmeester
Keyword(s):  
Composition Range ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Intermolecular Forces ◽  
Spin Lattice Relaxation ◽  
Plane Rotation ◽  
Spin Lattice ◽  
A Value ◽  
Experimental Activation Energy ◽  
Thiophene Molecule

Benzene and thiophene are known to form solid solutions over the entire composition range; the present work demonstrates the orientational freedom of thiophene molecules in solid solution with excess perdeuterobenzene, through measurements of spin–lattice relaxation times. In addition, the atom–atom approximation to intermolecular forces yielded a potential energy profile for in-plane rotation of a thiophene molecule, embedded in a benzene lattice, which is consistent with the experimental activation energy for the relaxation. The second moment of the absorption signal for thiophene in perdeuterobenzene at 80 K was determined to be 0.66 G2, compared with a value of 0.42 G2 computed as the intramolecular contribution only for in-plane rotation

RELAXATION IN RUBY

1960 ◽  
Vol 38 (10) ◽  
pp. 1304-1317 ◽  
Author(s):  
R. A. Armstrong ◽  
A. Szabo
Keyword(s):  
Relaxation Time ◽  
Crystal Orientation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Cross Relaxation ◽  
Spin Lattice Relaxation ◽  
Signal Frequency ◽  
Spin Lattice ◽  
A Value ◽  
Frequency Ratios

The relaxation of the (1↔2) and (2↔3) transitions in chrome-doped Al2O3 (0.015%) has been studied at S-band, using a pulsed microwave method, over a range of crystal orientations in the magnetic field at temperatures of 77 deg;K to 50 deg;K, and at 4.2 deg;K and 1.6 deg;K. A T−7 variation of the relaxation time with temperature was found in the liquid nitrogen range. The relaxation time in this temperature range was found to be independent of crystal orientation, and for the (1↔2) transition was 50 microseconds at 77 deg;K. At liquid helium temperatures, harmonic cross relaxation was present over most of the range of the crystal orientation studied and was observed at harmonic-to-signal frequency ratios of 2:1, 3:2, and 1:2. The harmonic cross relaxation times were typically 10 to 100 times shorter than the lattice relaxation times, and were independent of temperature. At non-harmonic points at 4.2 deg;K, the spin–lattice relaxation could be described by one time constant, a value of 300 milliseconds being typical. At harmonic points anomalously long relaxation times as high as 12 seconds were observed.

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. %.

Water-Saturated Mesoporous MCM-41 Systems Characterized by 1H NMR Spin-Lattice Relaxation Times

1995 ◽  
Vol 99 (12) ◽  
pp. 4148-4154 ◽  
Author(s):  
Eddy Walther Hansen ◽  
Ralf Schmidt ◽  
Michael Stoecker ◽  
Duncan Akporiaye
Keyword(s):  
1H Nmr ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Water Saturated ◽  
Mcm 41

A longitudinally detected high-field ESR spectrometer for the measurement of spin–lattice relaxation times

2004 ◽  
Vol 167 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Ferenc Murányi ◽  
Ferenc Simon ◽  
Ferenc Fülöp ◽  
András Jánossy
Keyword(s):  
High Field ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
High Field Esr
Sign in / Sign up

Export Citation Format

Share Document