Transient Oscillations in NMR Cross-Polarization Experiments in Solids

Time-Domain Multiple-Quantum NMR

“…For finite systems the S magnetization is often observed to oscillate (158,161,162) This is a result of a change of sign in the coefficient of the terms in the second parentheses of (4.9). In the limit that this coefficient reaches a value equal and opposite to that in (4.9) then one attains the adiabatic (isentropic) limit for Hartmann-Hahn matching (4.11) This is just twice the magnetization in (4.10).…”

Ordering in nematic liquid crystals from NMR cross-polarization studies

“…Observation of dipolar oscillations during CP has been made by Mulleret al [16] in a single crystal of ferrocene. In liquid crystals such as MBBA (figure 2), 13 C spectra containing sharp well-resolved lines can be obtained using the CP sequence (figure 1a).…”

“…The value of´hγ C γ H 4π 2 r 3 CH µ is 22.68 kHz for r CH 1 1Å. Equation (1) modified [16] to take into account spin diffusion between the protons directly coupled to the carbon under consideration and the rest of the protons in the system as…”

“…Another approach that has been proposed and implemented is the use of a variant of the SLF 2D experiment that uses the transient oscillations observed during cross polarization [16,17] for estimating dipolar couplings [18]. Modifications to the standard crosspolarization pulse scheme such as the use of homonuclear decoupling during cross polarization (CP) and the use of polarization inversion have also been suggested [19,20].…”

Spin projection chromatography

“…In spite of the naive expectation that quantum dynamical interferences might be limited to simple systems close to its ground state, most of the advances were originated on Nuclear Magnetic Resonance (NMR) [7] which deals with spin-spin interactions much weaker than the thermal energy k B T . The discreteness of the spin system produces quantum beats that allow an efficient cross-polarization among different spin species [8]. In small bounded spin systems, such as molecules, the initial spreading out of a local excitation is followed by a revival known as Mesoscopic Echo [9] (ME) manifesting the reflection at the molecular boundaries.…”