Nuclear quadrupole coupling constants in liquids. Raman line shapes and2D spin–lattice relaxation in CDCl3and CDBr3

1975 ◽  
Vol 63 (2) ◽  
pp. 909-914 ◽  
Author(s):  
David A. Wright ◽  
Max T. Rogers
Keyword(s):  
Raman Line ◽  
Lattice Relaxation ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Line Shapes ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Sodium NMR in the trigonal phase of sodium hydrosulfide

1976 ◽  
Vol 54 (16) ◽  
pp. 1651-1659 ◽  
Author(s):  
Kenneth R. Jeffrey ◽  
Stanley L. Segel
Keyword(s):  
Phase Transition ◽  
Lattice Relaxation ◽  
Quadrupole Coupling Constant ◽  
Spin Lattice Relaxation ◽  
Trigonal Axis ◽  
Coupling Constant ◽  
Spin Lattice ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Trigonal Phase

Measurements of the sodium nuclear quadrupole coupling constant and spin–lattice relaxation time, while confined mainly to the trigonal phase, show the existence of the two known phase transitions at 358 and 113 K. The quadrupole coupling constant is 206 kHz at 358 K and decreases roughly linearly with decreasing temperature at a rate of about 0.66 kHz/K. The satellite peaks in the quadrupolar split powder pattern disappear above 358 K in the cubic phase. Below 130 K. where there is no known phase transition, the satellites broaden and again disappear but in this case it is because the fluctuation rate of the electric field gradient at the sodium site due to reorientation of the SH− ion is about equal to the quadrupolar splitting of the spectrum at this temperature. Only the resonance from the −1/2 ↔ 1/2 transition is observed down to 77 K.The spin–lattice relaxation of the sodium spins shows a very strong temperature dependence and a well-defined minimum similar to the previously observed results for the protons. The relaxation is caused by the nuclear quadrupole interaction made time dependent by the reorientation of the neighbouring SH− ions. A simple model calculation gives reasonable agreement between the calculated and experimental values of T1 at the minimum if the SH− ion is considered to move between two positions parallel and antiparallel to the trigonal axis. An extension of this model suggests that the lack of an enhanced relaxation rate at the 113 K phase transition may be a result of a parallel ordering of neighbouring SH− ions along the trigonal axis in the lowest temperature phase.

Applications of 95Mo N.M.R. Spectroscopy. XVIII. Relaxation Times, Quadrupole Coupling Constants and Partial Field Gradients in [Mo(CO)5L] Complexes

1988 ◽  
Vol 41 (9) ◽  
pp. 1457 ◽  
Author(s):  
RTC Brownlee ◽  
BP Shehan ◽  
AG Wedd
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Quadrupole Coupling Constant ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Scalar Coupling ◽  
Spin Lattice ◽  
Field Gradients ◽  
Pyridine Complex ◽  
Quadrupole Coupling

A study of ,95Mo spin-lattice relaxation times (T1) and linewidths of [Mo(CO)5L] complexes, where L = PPh3, AsPh3, SbPh3, pyridine and Cl-, has shown that the relaxation times are due entirely to the quadrupolar mechanism, with no scalar coupling contribution to linewidth where molybdenum is bonded to a quadrupolar nucleus. Based on the literature value of the quadrupole coupling constant obtained by n.q.r . for the PPh3 complex (1.972 MHz), the quadrupole coupling constants of the arsine and stibine complexes are determined to be 3.36 and 3.75 MHz respectively. These values, and that of the pyridine complex (2.80 MHz), are found to correlate with ligand partial field gradient parameters obtained from Mossbauer spectra of FeII complexes, and are rationalized in terms of metal- ligand bonding interactions. For Et4N [Mo(CO)5Cl], the correlation is very poor; this result is attributed to the effects of ion in solution.

NQR Study of AlBr3 Complexes with Donor-Acceptor O-Al Bond

1990 ◽  
Vol 45 (3-4) ◽  
pp. 237-242 ◽  
Author(s):  
Hideta Ishihara ◽  
Shouko Nakashima ◽  
Koji Yamada ◽  
Tsutomu Okuda ◽  
Alarich Weiss
Keyword(s):  
Phase Transitions ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Hindered Rotation ◽  
Spin Lattice ◽  
Quadrupole Coupling ◽  
Temperature Dependences ◽  
Donor Acceptor

Abstract81Br and 27Al NQR were observed in AlBr 3 complexes with 4-XC6H4 NO,(X = H, CI, Br, I, CH3 , and C2H5), C6H5COBr, (C6H5)2CO, and (C2H5)2O. In the 4-XC6H4 NO2 complexes, the 27Al quadrupole coupling constants (QCC's) were well correlated with the Hammett er p 's of the para-substituents, i.e., electron-withdrawing groups caused reduction of the charge density of O-Al bonds which resulted in large 27Al QCC's and vice versa. The temperature dependences of the 81Br NQR frequencies and quadrupolar spin-lattice relaxation times showed that the 4-C2H5C6H4NO2 and C6H5 COBr complexes undergo phase transitions at 154 K and around 200 K, respectively, and show hindered rotation of the AlBr3 groups at higher temperatures, and that the (C2H5) 2O complex reorients above ca. 120 K.

On the Nature of the “Bleaching out” Process of the 35Cl NQR Signals in 1,2,3-Trichlorobenzene

1990 ◽  
Vol 45 (3-4) ◽  
pp. 490-502 ◽  
Author(s):  
Silvia Wigand ◽  
Norbert Weiden ◽  
Alarich Weiss
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Ring Plane ◽  
Spin Lattice ◽  
H Nmr ◽  
Principal Axes ◽  
Quadrupole Coupling ◽  
Benzene Ring Plane

AbstractThe 35Cl NQR frequencies, linewidths, and spin-lattice relaxation times T1(35Cl) of 1,2,3-trichlorotrideuterobenzene were measured at various temperatures. The deuterated compound shows the same bleaching out phenomenon as 1,2,3-trichlorobenzene. Single crystal 2H NMR measurements were carried out at 295 and 193 K. The nuclear quadrupole coupling constants at room temperature are in the range of 175.8 ≦ e2qQh-1 (2H)/kHz ≦ 179.5, and the asymmetry parameters η in the range of 0.060 ≦ η (2H) ≦ 0.073. As for the principal axes of the electric field gradient tensor, it was found that Φzz(2H) is parallel to the C - D bond, Φyy (2H) is perpendicular to the benzene ring plane and Φxx(2H) lies in the ring plane. The linewidths of the 2H NMR satellites are idependent of temperature. For the undeuterated compound, the temperature dependence of T1(1H) was also measured. The mechanism leading to the bleaching out of the 35Cl NQR signals is discussed.

81Br Nuclear Quadrupole Relaxation in Aluminium Tribromide

1995 ◽  
Vol 50 (8) ◽  
pp. 737-741 ◽  
Author(s):  
Noriaki Okubo ◽  
Mutsuo Igarashi ◽  
Ryozo Yoshizaki
Keyword(s):  
Room Temperature ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Quadrupole Relaxation ◽  
Spin Lattice ◽  
Raman Process ◽  
Nuclear Spin Lattice Relaxation ◽  
Nuclear Quadrupole ◽  
Nuclear Quadrupole Relaxation

Abstract The 81Br nuclear spin-lattice relaxation time in AlBr3 has been measured between 8 K and room temperature. The result is analyzed using the theory of the Raman process based on covalency. A Debye temperature of 67.6 K and covalency of 0.070 and 0.072 for terminal and 0.022 for bridging bonds are obtained. The correspondence of the latter values to those obtained from the NQR frequencies is low, in contrast to the previously examined compounds.

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