| Autor: |
Hediger, S., Meier, B. H., Ernst, R. R. |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 3/8/1995, Vol. 102 Issue 10, p4000, 12p |
| Abstrakt: |
We demonstrate that in solid-state nuclear magnetic resonance the Hartmann–Hahn cross-polarization efficiency in the presence of fast magic angle sample spinning can be improved by the application of rotor-synchronized amplitude-modulated radio-frequency irradiation during the mixing time (AMCP pulse sequences). The modulation reintroduces time-independent coupling elements between dressed eigenstates of the Floquet Hamiltonian which lead to flip–flop transitions. By numerical optimization, an optimal AMCP pulse sequence is designed which provides a significant improvement over conventional cross polarization. The matching condition can be broadened by rotor-synchronized 180° phase shifts to render the transfer less sensitive to exact matching of the applied radio-frequency field strengths. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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