scholarly journals The role of the glassy dynamics and thermal mixing in the dynamic nuclear polarization and relaxation mechanisms of pyruvic acid

2014 ◽  
Vol 16 (48) ◽  
pp. 27025-27036 ◽  
Author(s):  
M. Filibian ◽  
S. Colombo Serra ◽  
M. Moscardini ◽  
A. Rosso ◽  
F. Tedoldi ◽  
...  
Keyword(s):  
Relaxation Rate ◽  
Dynamic Nuclear Polarization ◽  
Pyruvic Acid ◽  
Nuclear Polarization ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Thermal Mixing ◽  
Spin Lattice

In pyruvic acid containing 15 mM trityl below 4 K 13C polarization and spin–lattice relaxation rates are proportional to the spin–lattice relaxation rate of electrons, suggesting an efficient thermal mixing scenario.

scholarly journals β-Radiation Detected NMR in Solid and Liquid Neon

1994 ◽  
Vol 49 (1-2) ◽  
pp. 27-30 ◽  
Author(s):  
F. Hilmer ◽  
A. Schirmer ◽  
H. Ackermann ◽  
P. Heitjans ◽  
H.-J. Stöckmann
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nuclear Polarization ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Rare Gases ◽  
Spin Lattice ◽  
Cold Neutrons ◽  
Spin Polarized ◽  
Liquid Neon

Abstract Spin-polarized β-active 23Ne (T1/2 = 37.2s) nuclei were created by capture of polarized cold neutrons in solid and liquid neon. The angular asymmetry of the β-radiation was used to monitor the nuclear polarization. From nuclear magnetic resonance curves the value for the dipole moment |μ(23Ne)| = 1.079(1) n.m. (uncorrected) was obtained which is more precise than the literature value. Comparing the measured spin-lattice relaxation rates with those of stable 21Ne the nuclear quadru­pole moment of 23N e was determined. It agrees with a shell model calculation. The feasibility of 23Ne-β-NMR for investigations in condensed rare gases in demonstrated.

Effect of Deuteration on the Phase Transitions and on the Critical Dynamics in Ammonium Hexachlorometallates

1994 ◽  
Vol 49 (1-2) ◽  
pp. 232-246 ◽  
Author(s):  
J. Pelzl ◽  
C. Dimitropoulos
Keyword(s):  
Relaxation Rate ◽  
Structural Changes ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Ammonium Ion ◽  
Relaxation Rates ◽  
Spin Lattice Relaxation Rate ◽  
Spin Lattice ◽  
Slowing Down ◽  
Lattice Relaxation Rate

Abstract Recent and novel data obtained from chlorine NQR measurements on natural and deuterated (NH4)2MCl6 compounds are discussed with special regard to the influence of the ammonium-ion dynamics on the structural stability of these crystals. The temperature dependence (4.2 K to 350 K) of the chlorine NOR frequency vQ and relaxation rates T1-1 , T2-1 obtained from the natural ammonium salts of Sn, Pd, Os, Pb, Te, Se and from the deuterated salts of Sn, Te and Se are analysed. Slight deviations from the normal temperature behaviour of vQ and T1-1 are found in Sn, Pd and Os compounds which stay cubic in the whole temperature range. The ammonium compounds of Pb and Te undergo a structural transformation between 80 K and 90 K from the cubic to a trigonal phase which is distinguished by the preservation of the single line spectrum of the chlorine NQR below rel. The observed divergence of T1-1 at the transition point can be described in terms of a spin-phonon process in the presence of an overdamped soft mode. Deuteration of (NH4)2TeCl6 only slightly affects the transition of Tc2 but leads to new structural changes at lower temperatures. Whereas the natural compound stays trigonal down to 4.2 K the deuterated crystal undergoes two additional structural transformations at Tc2 = 48 K and Tc3 = 28 K which are correlated with a slowing down of the deuteron motion. Approaching Tc2 from above, the spin-lattice relaxation rate and the spin-spin relaxation rate of the chlorine NQR exhibit distinct anomalies which are attributed to limited jumps of the octahedron in a shallow potential. The barrier height of this potential deduced from the chlorine NQR spin-lattice relaxation rate is 400 K. The transition at Tc2 is explained by the condensation in one minimum of this potential. At Tc3 a long range correlation is formed which is accompanied by a rotation of the octahedron about its fourfold axis. A similar mechanism is adopted for the transitions observed in (NH4)2SeCl6 at Tc= 24 K and in (ND4)2 SeCl6 at Tc = 48 K.

Cu(1) NQR in Y1 _ xPrxBa2Cu3O7

1996 ◽  
Vol 51 (5-6) ◽  
pp. 797-800 ◽  
Author(s):  
Takashi Ohno ◽  
Hironori Nishihara ◽  
Kuniyuki Koyama ◽  
Hiroshi Yasuoka
Keyword(s):  
Temperature Dependence ◽  
Relaxation Rate ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice

Cu(1) NQR spectra of the CuO chain site in Y1 _ xPrxBa2Cu3O7 (x = 0.1 and 0.2), and the 63Cu(1) NQR spin-lattice relaxation rates 1/T1 in Y0.9Pr0.1Ba2Cu3O7 have been measured. The half widths are about three times wider than those of the pure YBa2Cu3O7 . The peak frequencies are lowered by the Pr doping. This seems to indicate a decrease of on-site holes at the Cu(1) site. The relaxation rate 1/T1 is found to obey the same temperature dependence, 1/T1 = aT + bT3 as reported for pure YBa2Cu3O7.

Theory of the Knight Shift and Spin-Lattice Relaxation Rate in Pu-115

2005 ◽  
Vol 893 ◽  
Author(s):  
Yunkyu Bang ◽  
Matthias J. Graf ◽  
Nicholas J. Curro ◽  
Alexander J. Balatsky
Keyword(s):  
Relaxation Rate ◽  
Knight Shift ◽  
Lattice Relaxation ◽  
Spin Fluctuations ◽  
Spin Lattice Relaxation ◽  
Oxide Superconductors ◽  
Relaxation Rates ◽  
Spin Lattice Relaxation Rate ◽  
Spin Lattice ◽  
Lattice Relaxation Rate

AbstractWe calculated the Knight shift and spin-lattice relaxation rates of Pu-115 compounds assuming d-wave superconductivity in the presence of strong impurity scattering. We discuss the implications for recent measurements of the spin-lattice relaxation rate in the Pu-115 compound PuRhGa5 by Sakai and coworkers [J. Phys. Soc. Jpn. 74, 1710 (2005)] and present a prediction for the corresponding Knight shift. In addition, we noticed a significant round-off of the spin-lattice relaxation rate 1/T1 just above the superconducting transition temperature that is not observed in the sister compound PuCoGa5. It appears that in PuRhGa5 superconductivity is mediated by spin fluctuations, too. This provides additional support to the scenario of superconducting pairing mediated by spin fluctuations in the Pu-115 compounds similar to the Ce-115 compounds and the high-temperature copper-oxide superconductors.

scholarly journals Nuclear magnetic resonance relaxation studies of the interaction of ligands with the monomer and tetramer forms of formyltetrahydrofolate synthetase

1988 ◽  
Vol 251 (1) ◽  
pp. 89-93 ◽  
Author(s):  
C H Yeh ◽  
D A Hanna ◽  
G W Everett ◽  
R H Himes
Keyword(s):  
Relaxation Rate ◽  
Lattice Relaxation ◽  
Monovalent Cation ◽  
Ammonium Nitrogen ◽  
Spin Lattice Relaxation ◽  
Monovalent Cations ◽  
Relaxation Rates ◽  
Ammonium Ions ◽  
Formyltetrahydrofolate Synthetase ◽  
Spin Lattice

Previous work using n.m.r. spectroscopy to investigate the binding between formyltetrahydrofolate synthetase and its ligands was done using the catalytically active tetrameric form of the enzyme. By removal of specific monovalent cations the tetramer dissociates to four identical, catalytically inactive monomers, which are capable of binding nucleotides with affinities similar to those obtained with the tetramer. In the studies reported here, we examined the interaction of metal-nucleotide, formate and monovalent cations with the monomer using n.m.r. relaxation measurements. We were able to demonstrate that formate binds to the monomer. The spin-lattice relaxation rate (1/T1) of the formate carbon in the monomer. M2+.ADP. formate complex is enhanced when Mg2+ is replaced by Mn2+. By assuming that the exchange of formate is not rate-limiting and that tau c of the monomer is the same as that of the tetramer, the distance between the Mn2+ and the formate carbon was calculated and found to be similar in the monomer and tetramer complexes. The spin-lattice relaxation rates of [13C]trimethylammonium ion (an inactive monovalent cation), [13C]methylammonium and [15N]ammonium ions (both active monovalent cations), were measured in the presence of tetramer, MnADP and formate. The relaxation rates of methylammonium and ammonium ions were enhanced under these conditions whereas the relaxation rate of trimethylammonium ion was not. The results indicate that the active monovalent cations bind near the MnADP binding site. A distance from the Mn2+ to the ammonium nitrogen of between 0.5 and 0.6 nm was calculated.

The nuclear spin-lattice relaxation of an amorphous Hubbard model

1994 ◽  
Vol 72 (9-10) ◽  
pp. 658-667
Author(s):  
K. L. Liu
Keyword(s):  
Hubbard Model ◽  
Temperature Dependence ◽  
Relaxation Rate ◽  
Nuclear Spin ◽  
Low Temperatures ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Nuclear Spin Lattice Relaxation

We study the temperature dependence of the nuclear spin-lattice relaxation rate, (1/T1), of a structurally disordered Hubbard model for different electronic concentration ne, and for various interaction strength U. The relaxation process is assumed to be caused by the hyperfine Fermi contact interaction. The required electronic spin correlation function is studied up to the fourth order in hopping, and a Gaussian approximation is constructed. Two types of transfer integral have been examined: (1) quasi-exponential, and (2) Gaussian. At half-filling (ne = 1), the relaxation rate shows a strong U dependence at low temperatures. For large U, (1/T1) drops markedly when holes are introduced into the system at low temperatures, and its temperature dependence becomes weak when ne reaches 0.8. We also calculate the spin susceptibility and examine the ne dependence of the Korringa relation. We compare the relaxation rates with those for the two-dimensional Hubbard model with nearest-neighbor hopping on a square lattice, and contact is made with the recent NMR study of Sr-doped La2CuO4 at high temperatures.

Dynamic nuclear polarization and spin-lattice relaxation of the proton spins in Ca(OH)2

Physica B+C ◽  
1987 ◽  
Vol 145 (2) ◽  
pp. 153-164
Author(s):  
C.M.B. van der Zon ◽  
J. Marks ◽  
W.Th. Wenckebach ◽  
N.J. Poulis
Keyword(s):  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

scholarly journals Temperature and Pressure Variation of the Cl-NQR in A2PbCl6-Crystals

1986 ◽  
Vol 41 (1-2) ◽  
pp. 311-314 ◽  
Author(s):  
Y. M. Seo ◽  
J. Pelzl ◽  
C. Dimitropoulos
Keyword(s):  
Relaxation Rate ◽  
Room Temperature ◽  
Lattice Relaxation ◽  
Pressure Variation ◽  
Mixed Crystals ◽  
Spin Lattice Relaxation ◽  
Structural Transitions ◽  
Spin Lattice Relaxation Rate ◽  
Spin Lattice ◽  
Temperature And Pressure

The 35Cl NQR frequency and spin-lattice relaxation rate in the compounds A2PbCl6 (A = Cs, Rb, NH4, K) have been investigated in the range 4.2 K to 500 K, and as a function of pressure at room temperature. NQR experiments conducted on (K: NH4)2PbCl6 mixed crystals have been used to complete the NQR-frequency versus temperature diagram of K2PbCl6, revealing two structural transitions at Tc1 ≅ 358 K and at TC2 ≅ 333 K.

Analysis of Spin Polarisation Transients in Periodically Photo-excited Triplet States

1975 ◽  
Vol 30 (5) ◽  
pp. 571-582 ◽  
Author(s):  
C. J. Winscom
Keyword(s):  
Lattice Relaxation ◽  
Rectangular Pulse ◽  
Decay Rates ◽  
Spin Lattice Relaxation ◽  
Pulse Excitation ◽  
Triplet States ◽  
Relaxation Rates ◽  
Spin Sublevel ◽  
Spin Lattice ◽  
The Individual

Abstract The behaviour of spin sublevel populations with time following periodic photo-excitation is ex-amined. The treatment is limited to conditions of magnetic field strength and temperature for which the spin lattice relaxation rates dominate the individual spin sublevel decay rates. The response of the system to three modes of excitation is considered: (i) continuous excitation using a time-independent intensity (ii) periodic rectangular pulse excitation and (iii) periodic waveform excitation. A convenient correspondence between the various forms of solutions is pointed out. The requirements of an experiment to determine spin-lattice relaxation rates in organic triplets at 77 K are discussed.

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