Relaxation time spin-lattice, heteronuclear chemical

Temperature Dependence of Spin-Lattice Relaxation. The spin-lattice relaxation rate T ) is comprised of various contributions to the relaxation process, including homo- and heteronuclear dipolar interactions, quadrupolar interactions, chemical shift anisotropy, spin-rotation, and others (10). When the relaxation mechanism is dominated by inter- and intramolecular dipole-dipole interactions, the will increase with temperature, pass through a maximum, and decrease with increasing temperature. Since the relaxation rate is the inverse of the relaxation time, the Ti will decrease, pass through a minimum (Timin), and then increase with increasing temperature (77). The T lmin values are proportional to the internuclear distances. 

Heteronuclear chemical shift correlation techniques can be used to infer spin-lattice relaxation times of the protons attached to the observe nucleus (39). This is accomplished by saturation of the protons and observe nucleus followed by a variable time t (saturation recovery) during which the observe nucleus is continued at saturation (by repeated pulsing) and the attached proton remagnetizes. This process is followed by the normal H/X 2D shift correlation experiment. The t-dependence of the 2D peak intensities is then used to extract H T s by exponential analysis. This approach can be used to extract proton Ti s in polymers via observation of their attached obtaining motional data nor-... 

D J-resolved NMR experiments are a conceptual amalgamation of two topics discussed above, the /-modulated spin echo and the two-dimensional characteristic of the spin—lattice relaxation experiments. As the name of these experiments implies, scalar coupling information, /, will be displayed in the one frequency domain chemical shift information will be presented in the second frequency domain. The simplest 2D/ experiments sort chemical shift information in the detected time domain, labeled by convention, while the heteronuclear scalar couplings of each carbon are sorted into the indirectly determined time domain, tj (do not be confuse lower case h with the spin—lattice relaxation time, Tj). 

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