[en] The study of the electronic relaxation by means of Moessbauer spectroscopy is reviewed. After a general discussion on the Moessbauer lineshape problem, the relaxation effects are considered within the stochastic and superoperators theories. Simulated and experimental relaxation spectra are also presented. (author)

[en] We solve the dynamics of quantum spin chains when the initial condition is prepared as a spatially inhomogeneous state of the magnetization. Particularly long-lived states are found for which the relaxation time diverges and the whole relaxation process slows down as a consequence of constructive interference at degenerate stationary points. These states may be of interest for performing quantum computation

[en] The basic principles that must be known to interpret NMR images, are exposed. After an analysis of the fundamental parameters (T1 and T2 relaxation time particularly), the main elements necessary to analyse a Spin Echo image are presented

[en] Although fragility of glass forming liquids is traditionally related to cooperativity in molecular motion, the connection between those parameters remains unclear. In this paper we present the estimates of cooperativity (heterogeneity) length scale obtained from the boson peak spectra. We demonstrate that agrees well with the dynamic heterogeneity length scale for the structural relaxation estimated by 4- dimensional NMR, justifying the use of . Presented analysis of large number of materials reveals no clear correlation between and fragility. However, there is a strong correlation between the cooperativity volume 3 and the activation volume measured at Tg. This observation suggests that only the volume (pressure) dependence of structural relaxation time correlates directly with the cooperativity size. However, the pure thermal (energetic) contribution to the structural relaxation, the so-called isochoric fragility, exhibits no correlation to the heterogeneity length scale, or the amount of structural units in 3. The presented results call for a revision of traditional view on the role of cooperativity/heterogeneity in structural relaxation of glass forming systems.

[en] The authors present their preliminary experience in the characterization of atherosclerotic lesions and thrombi according to the parameters employed in MRI, namely longitudinal (T1) transversal (T2) relaxation times and proton density. (author). 8 refs.; 3 figs

[en] The spin relaxation times for different molecular structures have been calculated. Calculated relaxation times as a function of temperature are presented

[en] In this book it is explained how images are performed in nuclear magnetic resonance tomography. Therefore detailed discussions are deveted to the physical background, the possibilities for influencing of the images by the proper choice of pulse sequences, the spatial localization of the NMR signals and the clinical applications. (author). 323 refs.; 138 figs.; 2 tabs

[en] The decay of nuclear spin-spin energy has been studied in the mixed state of vanadium and anomalously rapid relaxation rates are found as compared to the rates for spin-lattice relaxation of Zeeman energy. The experiment was performed by adiabatically demagnetizing the spins in the rotating frame at a field larger than H/subc/₂ and then cycling the field to bring the sample into the mixed state for a variable time. The residual dipolar energy is detected, once the field is raised, by adiabatically remagnetizing the sample on resonance. I show that the relaxation observed, after the vortices are pinned, is due to a cross relaxation of a spin energy associated with the magnetic field gradients in the mixed state and the dipolar energy which is in semiequilibrium with the quadrupole energy. This process is mediated by a current of magnetization, proportional to the diffusion coefficient D, which is driven by the field gradients and uses dipolar energy as a heat sink. Using a field distribution in the mixed state calculated by Marcus, I find D = 2.8 +- 0.9 x 10^-12 cm² sec^-1 from the measurements of the relaxation rate of dipolar energy and of the quadrupole system heat capacity. This measurement of D is the first for a metal or for nuclei with I > 1/2 and is twice the value predicted by the moment-moment calculation of Redfield and Yu. In the presence of large field gradien-ts, dynamic quenching of the diffusion is observed

No abstract available

[en] The effect of a finite polarisation relaxation time on the transverse structure of the optical field of a wide-aperture laser is considered. The conditions are found for the emergence of periodic autowaves for positive and negative frequency detuning. These conditions are shown to depend strongly on the cross-relaxation rate. It is established that the dynamics of finite-aperture lasers at high cross-relaxation rates is satisfactorily described by simplified models in which the polarisation is adiabatically eliminated. (lasers)