Nuclear spin relaxation rate

A common assumption in the relaxation theory is that the time-correlation function decays exponentially, with the above-mentioned correlation time as the time constant (this assumption can be rigorously derived for certain limiting situations (18)). The spectral density function is then Lorentzian and the nuclear spin relaxation rate of Eq. (7) becomes ... 

Kruk and co-workers formulated, in analogy with the inner-sphere case, the expression for the nuclear spin relaxation rate of solvent nuclei, as... 

It is pertinent to comment here on the collapse of the Nuclear spin relaxation rate seen below Tc in NMR experiments. When nuclear spins in a material are aligned by an external magnetic field they can relax to equilibrium by causing... 

The interaction of the unpaired electron on the paramagnetic metal ion with that of the nuclear spin is analogous to the nuclear-nuclear spin complex commonly observed in nuclear mimetic resonance spectroscopy. Thus, the electron-spin relaxation (Te) affects the nuclear-spin relaxation-rates (T, and T2). Eqs. 3 and 4, describing the contribution to the nuclear relaxation rate from the component spin on the paramagnetic species were derived by Solomon and Bloembergen ... 

By the same experimental technique, the temperature dependence of the nuclear spin relaxation rates was investigated for the radical cations of dimethoxy- and trimethoxybenzenes [89], The rates of these processes do not appear to be accessible by other methods. As was shown, l/Tfd of an aromatic proton in these radicals is proportional to the square of its hyperfine coupling constant. This result could be explained qualitatively by a simple MO model. Relaxation predominantly occurs by the dipolar interaction between the proton and the unpaired spin density in the pz orbital of the carbon atom the proton is attached to. Calculations on the basis of this model were performed with the density matrix formalism of MO theory and gave an agreement of experimental and predicted relaxation rates within a factor of 2. 

Nuclear spin relaxation measurements were made of single crystals at between 150 and 1500K, under an O partial pressure of latm. The nuclear magnetic resonance spectrum consisted of a doublet which resulted from 2 different orientations of the electric field gradient tensor at 2 different Ti sites in the unit cell of the rutile lattice. The electric field gradient tensor was due to the 6 surrounding q2- ions, which formed a stretched octahedron. From the temporal evolution of the nuclear spin relaxation rate after a step-wise change in the 0 partial pressure, 2 different types of motion of the intrinsic defects were... 

Petrov et al. have presented a variable temperature solid-state NMR investigation of cryptophane-Exhloroform and cryptophane-Erdichlorometh-ane inclusion complexes.The line shapes and nuclear spin relaxation rates were analysed in terms of the distribution of C-D bond orientations and the time scale of the guest dynamics. It was found that encaged chloroform produces broad spectra, and that its reorientation is relatively slow with a correlation time of 0.17 ps at 292 K. In contrast, the line shapes of encaged dichloromethane were narrow and the motion of this guest molecule was fast with a correlation time of 1.4 ps at 283 K. The NMR data were complemented by an X-ray diffraction study of the cryptophane-E dichloro-methane structure, which was utihsed in the analysis of the NMR parameters. 

Ahn RMC, van den Eijnde JPHW, Verhaar BJ. (1983) Calculation of nuclear spin relaxation rate for spin-polarized atomic hydrogen. Phys. Rev. B 27 5424-5432. 

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