Nuclear spin-lattice relaxation rate

A more general theory for outer-sphere paramagnetic relaxation enhancement, valid for an arbitrary relation between the Zeeman coupling and the axial static ZFS, has been developed by Kruk and co-workers (96 in the same paper which dealt with the inner-sphere case. The static ZFS was included, along with the Zeeman interaction in the unperturbed Hamiltonian. The general expression for the nuclear spin-lattice relaxation rate of the outer-sphere nuclei was written in terms of electron spin spectral densities, as ... 

Fig. 7. H water proton relaxivity i.e., the nuclear spin-lattice relaxation rate per mM of metal, plotted as a function of the magnetic field strength expressed as the proton Larmor frequency for aqueous solutions of manganese(H) and iron(HI) ions at 298 K. (A) 0.10 mM manganese(II) chloride in 2.80 M perchloric acid (B) 0.1 mM aqueous manganese(H) chloride at pH 6.6 (C) 0.5 mM iron(HI) perchlorate in 2.80 M perchloric acid (D) 0.5 mM iron(IH) perchlorate in water at pH 3.1 (F) 2.0 mM Fe(HI) in 2.0 M ammonium fluoride at pH 7, which causes a distribution of species dominated by [FeFe]"-.

Abstract Spatially-resolved NMR is used to probe antiferromagnetism in the vortex state of nearly optimally doped high-rc cuprate H2Ba2CuC>6+a (Tc = 85 K). The broadened 205Tl-spectra below 20 K and the temperature dependence of the enhanced nuclear spin-lattice relaxation rate 205 Tfl at the vortex core region indicate clear evidences of the antiferromagnetic order inside the vortex core ofTl2Ba2Cu06+J. 

Figure 13 Field dependence of the Se nuclear spin-lattice relaxation rate in...

We have argued in this chapter that the iSf-LDOS (on which the nuclear spin-lattice relaxation rate of metals depends) is a useful concept to discuss variations in surface reactivity, bonding, and electrode potential effects among a series of related catalysts, in heterogeneous as well as in electrochemical catalysis. The f-LDOS is a... 

In general the Cooper pairs in conventional superconductors induced by phonons have. -symmetry where the gap opens uniformly on the Fermi surface and the temperature dependence of physical quantities below Tc is exponential. On the other hand, when the attractive force originates from spin or electron charge fluctuations, the Cooper pair has p- or d-wavc symmetry where the gap disappears on lines or points on the Fermi surface and the physical quantities have power-law temperature dependences. The quantities that are measured by NMR and nuclear quadrupole resonance (NQR) are the nuclear spin-lattice relaxation rate, 1 / T, the Knight shift, K, the spin echo decay rate, 1/T2 and the NQR frequency, vq. The most important quantities, K and 1/77 for the determination of the symmetry of the Cooper pairs are reviewed in the following sections. 

Figure 22. Temperature dependence of the nuclear spin-lattice relaxation rates for CO adsorbed on (A) Pt (B) Pt/Ru-14 (C) Pt/Ru-35 (D) Pt/Ru-52. Insets show the double-Gaiissian deconvolution. Relaxation rates are measured at the peak positions indicated by the arrows. (Reprinted with permission from Copyright 2002 Am. Chem. Soc.)...

Whereas the paramagnetic shift of the nuclear magnetic resonance frequency for a given applied field is related to the strength of the local hyperfine field at the nuclear site, induced by the electronic moments, the nuclear spin-lattice relaxation rate yields information about the low-frequency spectrum of thermally induced spin fluctuations. The influence of pair-correlation effects on the NMR relaxation in paramagnets was analysed experimentally and theoretically by... 

Fig. 79. Temperature dependences of the nuclear spin-lattice relaxation rate in a double-logarithmic plot against T for (a) Cu in CeCu Sij, (b) Be in UBeij and (c) Pt in UPtj. Data in (a) and (c) are from Asayama et al. (1988) data in (b) are from MacLaughlin et al. (1984).

When using the temperature dependence of the nuclear spin-spin or nuclear spin-lattice relaxation rate to study molecular motion, as is the case with the surface diffusion we are dealing with here, there exist soolled strong and weak collision limits. Different mathematical relationships are needed to describe these limits. Consider the nuclear spin-spin relaxation rate (1 / T2) as measured by a conventional Hahn-echo pulse sequence, and suppose that Aa> is the amplitude of the local field fluctuation responsible for relaxation. Also assume that r is the correlation time for the motion, say a jump, which causes the local field to fluctuate. The strong collision limit is defined such that... 

It is known (Blumberg 1960, Tse and Hartmann 1968, McHenry et al. 1972) that the kinetics (308) is typical for disordered systems in which a strong inhomogeneous NMR line broadening takes place and nuclear spin diffiision is hampered due to the Larmor frequencies differences of the nuclear spins located in the neighbouring crystal lattice sites. In such systems the nuclear spins at low temperatures relax directly via paramagnetic centers, well coupled with phonons. When paramagnetic centers with 5 = are randomly distributed in a crystal lattice, the nuclear spin-lattice relaxation rate is determined as follows ... 

The nuclear spin—lattice relaxation rate Ri = Tj" and spin—spin relaxation rate R2 =, where Tj and T2 account for the longitudinal and transversal... 

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