Zeeman enhanced nuclear

This produces cross-terms that give the enhanced nuclear Zeeman interaction term... 

A study of enhanced nuclear Zeeman tensor Y has been made in low magnetic fields (B = 100 gauss)2. In a previous paper , we extended the study to higher values of B where the enhanced Zeeman interaction becomes comparable to the pseudo-quadrupole interaction. While our fit was insensitive to the value of Yy (Yy /2iT = 4.98 kHz/g), we obtained... 

A more general theory for outer-sphere paramagnetic relaxation enhancement, valid for an arbitrary relation between the Zeeman coupling and the axial static ZFS, has been developed by Kruk and co-workers (96 in the same paper which dealt with the inner-sphere case. The static ZFS was included, along with the Zeeman interaction in the unperturbed Hamiltonian. The general expression for the nuclear spin-lattice relaxation rate of the outer-sphere nuclei was written in terms of electron spin spectral densities, as ... 

One key aspect of ENDOR spectroscopy is the nuclear relaxation time, which is generally governed by the dipolar coupling between nucleus and electron. Another key aspect is the ENDOR enhancement factor, as discussed by Geschwind [294]. The radiofrequency frequency field as experienced by the nucleus is enhanced by the ratio of the nuclear hyperfine field to the nuclear Zeeman interaction. Still another point is the selection of orientation concept introduced by Rist and Hyde [276]. In ENDOR of unordered solids, the ESR resonance condition selects molecules in a particular orientation, leading to single crystal type ENDOR. Triple resonance is also possible, irradiating simultaneously two nuclear transitions, as shown by Mobius et al. [295]. 

The Pr ground state nuclear spin levels consist of three levels split by the second-order hyperfine interaction and the relatively small nuclear electric quadrupole interaction. In non-zero magnetic fields each of these levels is additionally split due to the enhanced Zeeman interaction (see Fig. 4), The Hamiltonian of this system has been given by Teplov. ... 

In principal, resolution of Individual carbon resonances in bulk polymers, allows relaxation experiments to be performed which can be Interpreted in terms of main chain and side chain motions in the solid. In addition to the spin-lattice relaxation time in the Zeeman field, the spin-spin relaxation time and nuclear Overhauser enhancement, other parameters providing data on polymer dynamics include the proton and carbon spin-lattice relaxation times in the rotating-frame, T p, the cross-relaxation time Tqr, and proton relaxation in the dipolar field. Schaefer and Stejskal have carried out pioneering work in exploring polymer dynamics using solid-state NMR techniques. Measurement of T values in glassy PMMA at ambient temperature reveals that the a-CH3 carbon relaxes in <0.1s, the ester methyJL and methylene carbons in ca. Is and the two non-protonated (carbonyl and quaternary) carbons in ca. 10s. These results are consistent with the onset of internal reorientation of a-CH3 at this temperature relatively... 

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