The elegant 2D multiquantum (MQ) MAS NMR has been applied to investigate the coordination of Al atoms in SAPO-34. The results show that the effects of the template and/or water on the coordination of Al atoms are sig...The elegant 2D multiquantum (MQ) MAS NMR has been applied to investigate the coordination of Al atoms in SAPO-34. The results show that the effects of the template and/or water on the coordination of Al atoms are significant, which lead to the formation of various Al species. Up to four kinds of Al species are distinctly resolved.展开更多
It is demonstrated in terms of heteronuclear coupling systems AX_n (n=1, 2 and 3) that multiple quantum (MQ) transitions of various orders can be displayed in the perturbation of a weakly continuous wave (CW) R. F. fi...It is demonstrated in terms of heteronuclear coupling systems AX_n (n=1, 2 and 3) that multiple quantum (MQ) transitions of various orders can be displayed in the perturbation of a weakly continuous wave (CW) R. F. field. The effect of CW frequency offset and R. F. field strength on the observed MQ transition is discussed. The one-dimensional (1-D) MQ NMR has some advantages, such as high sensitivity, easy assignment of its spectrum, only requiring 1-D Fourier transform. Therefore it has a broad prospect for application. The Raman effect produced by the CW irradiation is interpreted.展开更多
A multiple quantum coherence (MQC) with a given order subjected to its own relaxa-tion decay in the evolution period can be transferred into observable single quantum (SQ)coherences in the detection period, the MQ rel...A multiple quantum coherence (MQC) with a given order subjected to its own relaxa-tion decay in the evolution period can be transferred into observable single quantum (SQ)coherences in the detection period, the MQ relaxation time in a spin system, therefore, canbe directly measured by the 1-dimensional (1-D) Hahn echo method since the amplitudes ofSQC’s are modulated by the decayed MQC. This 1-D approach is an alternation to the 2-Dmeasurement for MQ relaxation time, the latter being somewhat time-consuming. The 1-Dapproaches can readily get rid of the inhomogeneous broadening of MQ lines. A method forselective measurement of various MQ relaxation times in AX_n systems (n=1,2, and 3) witha given MQ order is presented. Consequently, the cross correlation coefficients of the sys-tems, which are not accessible in the SQ relaxation study, can be determined.展开更多
基金We are grateful to the support of the National Natural Science Foundation of China and the Ministry of Science and Technology of China. We appreciate Dr. R. Fu (NHMFL Tallahassee) for his kind help regarding the MQ MAS NMR experiments.
文摘The elegant 2D multiquantum (MQ) MAS NMR has been applied to investigate the coordination of Al atoms in SAPO-34. The results show that the effects of the template and/or water on the coordination of Al atoms are significant, which lead to the formation of various Al species. Up to four kinds of Al species are distinctly resolved.
基金Project supported by the National Natural Science Foundation of China
文摘It is demonstrated in terms of heteronuclear coupling systems AX_n (n=1, 2 and 3) that multiple quantum (MQ) transitions of various orders can be displayed in the perturbation of a weakly continuous wave (CW) R. F. field. The effect of CW frequency offset and R. F. field strength on the observed MQ transition is discussed. The one-dimensional (1-D) MQ NMR has some advantages, such as high sensitivity, easy assignment of its spectrum, only requiring 1-D Fourier transform. Therefore it has a broad prospect for application. The Raman effect produced by the CW irradiation is interpreted.
基金Project supported by the National Natural Science Foundation of China.
文摘A multiple quantum coherence (MQC) with a given order subjected to its own relaxa-tion decay in the evolution period can be transferred into observable single quantum (SQ)coherences in the detection period, the MQ relaxation time in a spin system, therefore, canbe directly measured by the 1-dimensional (1-D) Hahn echo method since the amplitudes ofSQC’s are modulated by the decayed MQC. This 1-D approach is an alternation to the 2-Dmeasurement for MQ relaxation time, the latter being somewhat time-consuming. The 1-Dapproaches can readily get rid of the inhomogeneous broadening of MQ lines. A method forselective measurement of various MQ relaxation times in AX_n systems (n=1,2, and 3) witha given MQ order is presented. Consequently, the cross correlation coefficients of the sys-tems, which are not accessible in the SQ relaxation study, can be determined.
