Collective relaxation time, liquid state

The values of T range broadly, depending on the particular type of nucleus, the location of the nucleus (atom) within a molecule, the size of the molecule, the physical state of the sample (solid or liquid), and the temperature. For liquids or solutions, values of 10 2 102 s are typical, though some quadrupolar nuclei have (faster) relaxation times of the order of 1(H s. For crystalline solids, T values are much longer (Section 2.5). For now, just remember that the larger the value of 7j, the longer it takes for a collection of nuclei to reach (or return to) equilibrium. 

The dynamics of molecular motion in simple (i.e., nonviscous) liquids have long been of interest in their own right and because of their importance in mediating liquid state chemical reactions. Collective orientational relaxation times, which measure the return of partially aligned liquids to their isotropic equilibrium states and are usually in the 5-100-ps range, have been determined in many fluids from Rayleigh linewidths or optical Kerr... 

Polarization transfer has also been observed between HP supercritical xenon and organic solutes. HP xenon was collected as a solid and then transferred to a 3 mm borosilicate tube containing the organic molecule (toluene or biphenyl) at a field of 1 T to avoid relaxation. Proton enhancements were observed to be three (biphenyl) or seven (toluene) times the Boltzmann equilibrium level as measured at 2T and with the xenon polarization at 2%. Several proton acquisitions could be made because the xenon Ty was approximately 7.5 min. The authors suggest that the low cross-relaxation rates observed in both the liquid and now supercritical phases could lead to better polarization transfer in the solid state, albeit with a highly dispersed xenon, such as provided by freezing a supercritical or liquid solution. 

In this book, we collect a series of chapters dedicated to the state-of-art studies of optical spectroscopy in the time domain on complex liquids of different nature. In Chap. 1, a new nonlinear spectroscopic technique, 2D-Raman, is comprehensively reviewed. This is probably tbe most promising experimental tool able to collect truly new information on fast dynamics in liquid matter. Chapter 2 is dedicated to optical Kerr effect techniques and to the investigation of relaxation d5mamics in complex liquids, inclusive of relative slow collective... 

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