Longitudinal coherence transfer

The remaining two are the longitudinal spin order, which results when the macroscopic z magnetization of one nucleus (e.g., H) is opposite depending on the microscopic z magnetization (a or P) state of the other nucleus (e.g., 13C), and the identity (1) operator, which simply represents the vast majority of spins that cancel each other out and play no role in NMR experiments. Longitudinal spin order can be viewed as an intermediate state in coherence transfer 2 US- 21-S- 2I-S.r = 2SX z. Like z magnetization, it is not affected... 

NMR-SIM is very powerful simulation tool based on a density matrix approach and is designed to make low demands on computer resources. The spin system parameters consist of a small basic set of spin parameters chemical shift, weak/strong scalar J coupling, dipolar coupling, quadrupolar coupling, longitudinal and transverse relaxation time. Currently the calculated coherence transfer processes are limited to polarization transfer and cross polarization. 

The concept of longitudinal and transverse magnetization must be extended if the discussion of multi-pulse experiments is to include multiple quantum states and coherence transfer. The concept of coherence, the transition between two eigenstates, is preferable to using the expression transverse magnetization. Each transition may involve... 

A recent experiment that seems likely to assume considerable importance is unusual in not making use of coherence transfer, but rather using tj modulation to "label" longitudinal magnetizations involved in chemical exchange or cross-relaxation.The basic pulse sequence has the form ... 

The following transfers between longitudinal magnetization (/ and S ) and zero-quantum coherence (7 5 - I Sy) are possible during Hartmann-Hahn mbdng (see Section II) and must be considered in an analysis of the lineshapes of diagonal peaks and cross-peaks (Bazzo and Campbell, 1988). 

Fig. 7.2.31 Filters for homonuclear coherent magnetization transfer. All filters start from and end with longitudinal magnetization, (a) Selective excitation and reconversion of coherences with a nonselective mixing period, (b) Realization of a nonselective mixing period in a z filter via longitudinal magnetization, (c) Nonselective excitation and reconversion of coherences with a selective mixing period, (d) Realization of a selective mixing period by a multi-quantum filter, (e) Selective exchange of transverse magnetization within the multiplets of coupled homonuclear spin pairs by a homonuclear version of the INEPT method.

FIGURE 16.3 Contour plots of the longitudinal current spectra, Q(g, ) = computed from coherent dynamic structure factors for protein hydration water in the RNase crystal at 300 K [60]. The black lines trace the maxima of the two BriUouin side peaks in the spectra, one of which is dispersive (i.e., the excitation energy is wavevector transfer/length scale dependent), and the other nondispersive. 

---