MOLECULAR REORIENTATION IN FERROELECTRIC LITHIUM HYDRAZINIUM SULPHATE

The temperature dependence of the spin-lattice relaxation time T1 and of the second moment of the magnetic-resonance absorption signal has been determined for protons in powdered lithium hydrazinium sulphate over the range 80–480 °K. These measurements indicate that the hydrazinium ion is rigid only at very low temperatures. As the temperature is raised, the −NH3 group begins to undergo hindered rotation about the N–N axis with an activation energy of 4.2 kcal/mole and the effect of this motion on the line width becomes pronounced in the region of 85 °K. Further molecular reorientation begins above room temperature and is probably reorientation of the −NH2 group about either the N–N axis or the bisectrix of the H–N–H angle. Above 435 °K the hydrazinium ion begins to tumble about several axes and at 480 °K diffuses through the structure.

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1H NMR Study of Molecular Motions in Thiourea Pyridinium Halide Inclusion Compounds

Zeitschrift für Naturforschung A ◽

10.1515/zna-2003-1108 ◽

2003 ◽

Vol 58 (11) ◽

pp. 638-644 ◽

Cited By ~ 4

Author(s):

M. Grottel ◽

A. Pajzderska ◽

J. Wasicki

Keyword(s):

Inclusion Compounds ◽

Symmetry Axis ◽

Activation Parameters ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Spin Lattice Relaxation ◽

Hindered Rotation ◽

Pyridinium Cation ◽

Spin Lattice ◽

Nmr Study

The proton NMR second moment and spin-lattice relaxation time have been studied for polycrystalline inclusion compounds of thiourea pyridinium chloride, bromide, iodide and their perdeuterated analogues in a wide temperature range. The pyridinium cation reorientation around the pseudohexagonal C6’ symmetry axis over inequivalent barriers and hindered rotation of the thiourea molecule around its C=S bond have been revealed. The activation parameters of the both motions have been found.

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NUCLEAR MAGNETIC RELAXATION IN GAS MIXTURES

Canadian Journal of Physics ◽

10.1139/p62-108 ◽

1962 ◽

Vol 40 (8) ◽

pp. 1027-1035 ◽

Cited By ~ 10

Author(s):

D. Llewelyn Williams

Keyword(s):

Room Temperature ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Proton Spin ◽

Spin Lattice Relaxation ◽

Spin Lattice ◽

Gas Molecules ◽

De Broglie Wavelength ◽

Diffraction Effects ◽

Good Agreement

Measurements of the proton spin–lattice relaxation time using pulse techniques have been made on the hydrogen–nitrogen, hydrogen–neon, and hydrogen–helium systems from room temperature to 60° K. The results are in good agreement with the Oppenheim–Bloom theory and illustrate the importance of the radial distribution of the gas molecules and of diffraction effects associated with the de Broglie wavelength.

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81Br Nuclear Quadrupole Relaxation in Aluminium Tribromide

Zeitschrift für Naturforschung A ◽

10.1515/zna-1995-0805 ◽

1995 ◽

Vol 50 (8) ◽

pp. 737-741 ◽

Cited By ~ 2

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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Temperature-Independent Spin-Lattice Relaxation Time in Metals at Very Low Temperatures

Physical Review B ◽

10.1103/physrevb.5.2397 ◽

1972 ◽

Vol 5 (7) ◽

pp. 2397-2409 ◽

Cited By ~ 90

Author(s):

F. Bacon ◽

J. A. Barclay ◽

W. D. Brewer ◽

D. A. Shirley ◽

J. E. Templeton

Keyword(s):

Relaxation Time ◽

Low Temperatures ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Spin Lattice Relaxation ◽

Spin Lattice Relaxation Time ◽

Spin Lattice

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Relaxation und optische Kernspinpolarisation der Protonen in optisch angeregten Anthracen-Kristallen

Zeitschrift für Naturforschung A ◽

10.1515/zna-1968-0718 ◽

1968 ◽

Vol 23 (7) ◽

pp. 1068-1076 ◽

Cited By ~ 4

Author(s):

G. Maier ◽

H. C. Wolf

Keyword(s):

Room Temperature ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Spin Lattice Relaxation ◽

Triplet States ◽

Spin Lattice ◽

Low Field ◽

New Type ◽

Spin Polarisation ◽

Triplet Excitons

The influence of optically excited metastable triplet states on the spin lattice relaxation time T1 of protons in anthracene is investigated at room temperature. From the H0-field dependence of T1 in the presence of excited triplets we calculate the hopping time of triplet excitons τc=(5±1) · 10–12 sec. Especially in the low field region a new type of dynamic nuclear polarisation is observed. Triplet excitons, which are excited using unpolarized light produce via optical exciton spin polarisation an optical nuclear spin polarisation. Polarisation factors of more than 1000 are observed. Preliminary experiments with anthracene-tetracene mixed crystals are able to separate relaxation and polarisation effects due to mobile excitons from effects, which don’t need the mobility of excitons.

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Ionic Motion of Phenethylammonium Ion in [C6H5CH2CH2NH3]2 PbX4 (X = Cl, Br, I) as Studied by 1 H NMR

Zeitschrift für Naturforschung A ◽

10.1515/zna-1997-6-706 ◽

1997 ◽

Vol 52 (6-7) ◽

pp. 502-508 ◽

Cited By ~ 9

Author(s):

Takahiro Ueda ◽

Mariko Omo ◽

Katsuyuki Shimizu ◽

Hiroshi Ohki ◽

Tsutomu Okuda

Keyword(s):

Room Temperature ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Activation Energies ◽

Spin Lattice Relaxation ◽

Fold Axis ◽

Spin Lattice ◽

Jump Model ◽

Temperature Dependences ◽

Torsional Angles

Abstract The temperature dependences at 110 to 400 K of the : 1H spin-lattice relaxation time (7\) of the phenethylammonium ion in phenethylammonium lead(II) halides, [C6H5CH2CH2NH3]2PbX4 (X = Cl, Br, I), revealed that this ion shows reorientation of the NH3 moiety around the three-fold axis and torsional motion of the alkyl chain (CH2CH2). Below room temperature, the chloride and the bromide yielded two minima of 1H T1 originating from NH3 reorientation, whereas the iodide yielded only one minimum. These findings indicate that there are two kinds of NH3 sites in the chloride and bromide but only one in the iodide. The T1 minimum observed below room temperature gave similar activation energies of the NH3 reorientation, Ea = 15.7,15.1 and 15.5 kJ mol 1 for the chloride, bromide and iodide, respectively, suggesting that the corresponding NH3 groups are located at similar environments. Above room temperature, the T1 minimum in the chloride and bromide gave larger Ea values of the NH3 reorientation: Ea - 23.6 and 20.2 kJ mol-1 for the chloride and bromide, respectively. These findings suggest that the NH3 groups form stronger hydrogen bonding with halogen atoms (N-H ... X). Furthermore, the amplitude of the CH2CH2 motion is discussed, using the two sites jump model. The activation energies for the CH2CH2 motion in these compounds are almost equal (Ea = 29.1, 30.0 and 28.2 kJ mol -1 for the chloride, bromide and iodide, respectively), but that the torsional angles become larger in the order iodide ⪡ bromide<chloride.

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Rotational ordering and nuclear spin-lattice relaxation in solid methane

Canadian Journal of Physics ◽

10.1139/p78-157 ◽

1978 ◽

Vol 56 (9) ◽

pp. 1182-1189 ◽

Cited By ~ 21

Author(s):

G. Briganti ◽

P. Calvani ◽

F. De Luca ◽

B. Maraviglia

Keyword(s):

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Proton Spin ◽

Spin Lattice Relaxation ◽

Molecular Reorientation ◽

Spin Lattice ◽

Nuclear Spin Lattice Relaxation ◽

Special Cases ◽

Lower Temperature ◽

Lower Temperature Region

The proton spin-lattice relaxation time has been measured in solid CH4 down to 0.4 K. In the ordered phase at 9 < T < 20 K the relaxation process is induced by librons. The energy of the librons (~75 K) is in excellent agreement with the theoretical prediction by Yamamoto, Kataoka, and Okada. T1 has been found constant within experimental error between 0.4 and 9 K. The mechanism responsible for relaxation in this lower temperature region is attributed to the adiabatic molecular reorientation of the ordered T molecules. The cooling procedure has been found in special cases to affect the experimental results.

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2H NMR Study of Molecular and Electron Spin Dynamics in Paramagnetic [Co(H2O)6][SiF6]

Zeitschrift für Naturforschung A ◽

10.1515/zna-2000-1-230 ◽

2000 ◽

Vol 55 (1-2) ◽

pp. 173-177

Author(s):

Takahiro Iijima ◽

Motohiro Mizuno ◽

Masahiko Suhara

Keyword(s):

Water Molecule ◽

Room Temperature ◽

Spin Dynamics ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Spin Lattice Relaxation ◽

Spectral Simulation ◽

Spin Lattice ◽

H Nmr ◽

Nmr Study

The temperature dependences of 2H NMR spectra and the spin-lattice relaxation time T\ were measured for [Co(H2O)f,][SiF6]. The variation of the spectrum above room temperature can be explained by the reorientation of [Co(H2O)6]2+ about the C3 axis. The activation energy Ea and the jumping rate at infinite temperature K0 for the three site jump of [Co(H2O)6]2+ were obtained as 82 kJmol-1 and 2x 1017s-1 from the spectral simulation. Below room temperature, the spectral line shape was dominated by the 180° flip of the water molecule. The minimum of T1 caused by the 180° flip of the water molecule was observed at ca. 260 K. The jumping rate of the 180° flip of the water molecule was estimated from the 2H NMR T1 and the spectral simulation. Ea = 38 kJmol-1 and K0 = 6x 1015s-1 for the 180° flip of the water molecule were obtained from T1.

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