Transfer of coherence and effect of level shift caused by two-quantum excitation in a multilevel NMR system

金沢大学教育学部理科教育The phenomenon of transfer of coherence and the effect of level shift caused by two-quantum (TQ) excitation were studied on Al27 nuclei in Al2O3. Transfer of coherence between two single-quantum (SQ) transitions and that between SQ and three-quantum transitions were examined. It was observed that the coherences transfer periodically with frequency equal to one-half the TQ transient nutation frequency accompanied by phase shifts caused by the level shift. Experimental results are in good agreement with theoretical predictions. The effect of magnetic dipole interaction was also studied. A precise measurement was made on the shift of TQ resonance frequency and it was confirmed that no shift exists on the TQ resonance frequency contrary to the prediction based on the three-level model. © 1983 The American Physical Society

Coherence-transfer rotary echoes produced by double irradiation in a three-level NMR system

金沢大学教育学部理科教育A new type of spin echoes associated with periodic transfer of coherence has been observed in a three-level NMR system under irradiation with two rf fields which are exactly at resonance to the two single-quantum transitions. The echoes are observed for the two-quantum coherences as well as for the single-quantum ones. The echo-envelope decay is considerably lengthened by the double irradiation because of the quenching of the magnetic dipolar interaction. © 1980 The American Physical Society