NMR observation of temperature-dependent spin-lattice relaxation intrans-polyacetylene

1987 ◽  
Vol 36 (4) ◽  
pp. 2153-2157 ◽  
Author(s):  
F. Masin ◽  
G. Gusman
Keyword(s):  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Spin Lattice

1HNMR Study on the Motion of NH4+ in Ferroelectric NH4H(ClH2CCOO)2 and Mixed (NH4)1-xRbxH(ClH2CCOO)2 (x = 0.15)

2002 ◽  
Vol 57 (11) ◽  
pp. 883-887 ◽  
Author(s):  
M. Zdanowska-Fra̡czek ◽  
A. Kozaka ◽  
R. Jakubasb ◽  
J. Wa̡sickia ◽  
R. Utrechta
Keyword(s):  
Relaxation Time ◽  
Group Dynamics ◽  
Nmr Relaxation ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Spin Lattice

Temperature-dependent proton NMR relaxation time measurements have been performed at 60 MHz in order to study the NH4+ dynamics in ferroelectric NH4H(ClH2CCOO)2 and mixed Rbx(NH4)1-x(ClH2CCOO)2, where x = 0.15. The data indicate that the dominant relaxation mechanism for the NMR spin-lattice relaxation time T 1 in both crystals involves simultaneous NH4 group reorientation about their C2 and C3 symmetry axis in the paraelectric phase. Details of the NH4+reorientation have been inferred from analysis of temperature dependence of T1 assuming the Watton model. The activation parameters of the motionshave been determined.It has been found that the substitution of Rb does not change the activation parameters of the NH4 group dynamics.

A 35CL NQR Spin-Lattice Relaxation Study on the Motion of D4h Anions in [C(NH2)3]2PdCl4, [C(NH2)3]2PtCl4, and [C(NH2)3]AuCl4

1986 ◽  
Vol 41 (1-2) ◽  
pp. 416-420
Author(s):  
Yoshihiro Furukawa ◽  
Daiyu Nakamura
Keyword(s):  
Relaxation Times ◽  
Sharp Decrease ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
35Cl Nqr ◽  
The One ◽  
Increasing Temperature ◽  
Complex Anions

The temperature dependence of 35Cl NQR spin-lattice relaxation times T1ClQ was observed for the crystal of the title complexes. For the Pd(II) and Pt(II) complexes, the log T1ClQ vs. 103 T-1 curves having gentle positive gradients at lower temperatures decreased sharply with increasing temperature from ca. 150 and ca. 130 K, respectively. This sharp decrease of T1ClQ can be explained by the C4 reorientation of the D4h complex anions with the activation energy Ea of 34 kJ mol-1 for the former and 29 kJ mol-1 for the latter complex. These values agree well with those estimated from 1H T1 showing temperature dependent dipolar-quadrupolar cross relaxation. For the Au(III) salt, two of four 35Cl NQR lines showed a sharp decrease in T1ClQ from ca. 270 K, suggesting the onset of the C4 reorientation of the one kind crystallographically equivalent anions with Ea of 67 kJ mol-1.

Proton Relaxation in Various Copper (II) Complexes and Determination of the Singlet-Triplet Separation

1980 ◽  
Vol 35 (1) ◽  
pp. 92-97 ◽  
Author(s):  
H. D. Jannek ◽  
W. Midler-Warmuth
Keyword(s):  
Copper Complexes ◽  
Lattice Relaxation ◽  
Magnetic Behaviour ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Temperature Dependent ◽  
Spin Lattice

Abstract Proton spin-lattice relaxation rates have been measured at 30 MHz as a function of temperature for a large number of dimeric copper complexes with the ligands 8-hydroxyquinoline, pyridine-N-oxide, methyl and dimethyl pyridine-N-oxide, and quinoline-N-oxide. Two carboxylates and adducts of several complexes with various solvents have also been studied. In contrast to some compounds with a normal magnetic behaviour, for most complexes a temperature dependent relaxation has been observed which agrees well with the concept of a weak antiferromagnetic interaction between the two Cu2+ ions. The singlet-triplet separations or exchange integrals have been determined.

scholarly journals Vibronic Effects in Mossbauer Spectra: The 57Fe Quadrupole Splitting in FeCO3

1978 ◽  
Vol 31 (5) ◽  
pp. 397 ◽  
Author(s):  
DC Price
Keyword(s):  
Quadrupole Splitting ◽  
Lattice Relaxation ◽  
Vibronic Coupling ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
Symmetry Properties ◽  
Coupling Parameters ◽  
Magnetic Ions

The methods developed by Orbach and coworkers for calculating spin-lattice relaxation rates have been generalized to enable calculation of the effects of vibronic admixture between low-lying electronic states on observables, such as the Mossbauer quadrupole splitting, associated with magnetic ions in crystals. Emphasis is placed on the need to take proper account of the symmetry properties of the phonons until a late stage in the calculation. Application is made to the temperature dependence of the 57Fe quadrupole splitting in FeC03 , and it is concluded that, in general, vibronic coupling effects must be considered before static splitting parameters are extracted from experimental data relating to the temperature-dependent populations of electronic levels. The superposition model of the crystal field is employed to estimate the vibronic coupling parameters.

35Cl NQR Studies of Hydrogen Transfer in Crystalline p-Chlorobenzoic Acid

2000 ◽  
Vol 55 (1-2) ◽  
pp. 355-358 ◽  
Author(s):  
Taka-aki Nihei ◽  
Shin'ichi Ishimaru ◽  
Ryuichi Ikeda
Keyword(s):  
Hydrogen Transfer ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Chlorobenzoic Acid ◽  
Spin Lattice ◽  
H Nmr ◽  
Double Proton Transfer ◽  
Carboxylic Acid Dimer

35Cl NQR frequencies and spin-lattice relaxation times T1Q were measured in p-ClC6H4CO2H(PCB A) and p-ClC6H4CO2D(PCBA-d1) at 77-333 K. T1Q in PCB A gave a shallow minimum of 8.0 ms at ca. 110 K, which could be explained by a double proton transfer mechanism in the carboxylic acid dimer referring to 1H NMR data giving a T1H minimum at almost the same temperature. PCBA-d1, showed temperature dependent NQR frequencies quite analogous to those in PCBA, whereas their T1Q behaviour was quite different in its minimum value and its temperature as well as temperature gradient. These results were explained by suppressed deuteron tunnelling and the Ubbelohde effect.

Radio-Spectroscopic Studies of Magnetic Properties of High Temperature Superconductors

1990 ◽  
Vol 45 (3-4) ◽  
pp. 401-404
Author(s):  
E. Lippmaa ◽  
E. Joon ◽  
I. Heinmaa ◽  
V. Miidel ◽  
A. Miller ◽  
...  
Keyword(s):  
High Temperature Superconductors ◽  
Sharp Decrease ◽  
Lattice Relaxation ◽  
Spectroscopic Studies ◽  
Spin Fluctuations ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
Temperature Dependences ◽  
Powder Samples

Abstract We have performed 17O and 63Cu NMR measurements in YBa2Cu3O7-δ (δ ≈ 0.15) oriented powder samples at CuO2 plane sites Cu(2) and 0(2, 3) in the temperature range 10-300 K. The temperature dependent Knight shift K(T) and spin lattice relaxation rate T1-1-(T) of O(2, 3) yield K2T1T = const in accordance with the presence of free carriers at plane oxygen sites. A sharp decrease of T1-1 of Cu(2) below 120 K is associated with the opening of a gap in the spectrum of antiferromagnetic spin fluctuations of localized copper 3 d9 electrons. The comparison of different temperature dependences of spin densities at the Cu and O sites shows the presence of two nearly independent spin systems. A close similarity of YBa2Cu3O7-δ a with heavy fermion superconductors is discussed.

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