Chain spin moment

Here Ti is the spin-lattice relaxation time due to the paramagnetic ion d is the ion-nucleus distance Z) is a constant related to the magnetic moments, i is the Larmor frequency of the observed nucleus and sis the Larmor frequency of the paramagnetic elechon and s its spin relaxation time. Paramagnetic relaxation techniques have been employed in investigations of the hydrocarbon chain... 

If we were to have an isolated polymer chain with a single nuclear spin attached to each segment (the marked chain) crosslinked into an unmarked network, the second moment of the NMR line of that spin species would carry information relating to the separation of chain segments, and to their relative orientation with respect to the field direction. If the network were to be subjected to a bulk deformation, these geometrical parameters would be altered, and hence we would expect a corresponding change in the value of the experimentally measured... 

These moment studies have been performed on polymer systems such as polyethylene (or on penetrants in polymer systems) in which the interacting spins (protons or fluorines) reside on the same or on adjacent atoms. This allows essentially no freedom of variation in the internuclear vectors upon deformation of the network. The primary informational content therefore relates to independent segmental orientation distributions. By placing single spins on alternate segments, there should be much greater sensitivity to changes in the chain extension upon bulk deformation. 

The new backbone atom must now be checked for overlap with other atoms on the chain. The distance from every other atom is then calculated. If there is a spin on this atom, terms for the second moment summation are accumulated in this program loop as well. 

The angle dependence of the spin soliton in randomly oriented ladder poly-diactylene has also been investigated79 by pulsed HFEPR at 94 GHz. The shape of the 0-anisotropy-resolved nutation spectrum was discussed on the basis of the EPR transition moments and the differences between spin relaxation times. Reliable assignments of hyperfine couplings to the p-protons (P-H) of the alkyl side chains were achieved with the support of W-band ENDOR measurements. No significant orientational dependence of the 7i and Ti processes was found in terms of the isotropy of the p-H-hyperfine interaction. 

Nuclear spins and moments of ground and isomeric states are basic properties probing the structure and shape of atomic nuclei. The systematic experimental study of these quantities along isotopic and isotonic chains thus allows a mapping of the nuclear behaviour, to be compared with the predictions of different nuclear models. 

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