Gan, ZH
1990
Rotational Resonance in a Spin-Lock Field for Solid State NMR
Gan, Z.H. and Grant, D.M.
Chemical Physics Letters, 168 (3,4), 1990. Funded by a National Institute of Health research grant from the Institution of General Medical Science.
In the magic angle spinning NMR experiment, a rotational resonance phenomenon occurs whenever a spin-lock rf field is either equal to or twice the sample spinning speed. The resonance occurs in the rotating frame where the spin-lock field assumes the role of the "Zeeman" interaction and the chemical shift modulated by the sample rotation is the "radio frequency" irradiation. The importance of good rf field homogeneity to the experiment is shown.
Molecular and Structural Information from Variable-Angle Spinning NMR Dipolar Spectra of C-13/N-14 Systems
Gan, Z.H. and Grant, D.M.
Journal of Magnetic Resonance, 1990 (In press). Funded by National Institute of Health.
A sample-spinning solid-state NMR study of a spin-1/2 nucleus coupled to a quadrupolar nucleus is presented. Using a simple approach, the quadrupolar effect is expanded in terms of irreducible spherical tensor components up to / = 4. Information on the electric field gradient tensor orientation, dipolar coupling, and chemical-shielding tensor for the C-13/N-14 system can be obtained experimentally from the magic-angle and the off-magic-angle sample-spinning spectra. Satisfactory results are obtained by comparing the simulations with the experimental spectra of tetramethylpyrazine, dimethyglyoxime, and triethylenediamine.
1988
The Effect of Transverse Cross Relaxation of NMR Dipolar Spectra
Gan, Z.H.; Facelli, J.C. and Grant, D.M.
Submitted to J. Chem. Phys., 1988. Funded by US Department of Energy.
The C-13 dipolar powder spectra of C-13H3P-31O(OH)2 at room temperature and C-13H3F-19 at low temperature (T=25K) are reported. An intense peak is observed in the center of the Pake doublet. This phenomenon is explained by the transverse cross relaxation mechanism between the C-13 and either the P-31 or F-19 nuclei. The chemical shielding tensors and dipolar coupling constants of these two molecules are obtained by fitting the experimental spectra.
C-13 Dipolar Spectroscopy of Nitromethane
Solum, M.S.; Facelli, J.C.; Gan, Z.H. and Grant, D.M.
Submitted to Molecular Physics, 1988. Funded by US Department of Energy.
The C-13 low temperature (25K) dipolar spectrum of C-13H3N-14O2 is reported. The spectrum was fit and the principal values of the C-13 shielding tensor are given. The C-13 shielding tensor principal values are similar to those found in other C-13H3 groups. Also, the N-14 quadrupolar parameters and the direct dipolar couplings were obtained from the fit. Because of librational motions an effective trace term in the dipolar interaction has to be included in the fit.
Gan, ZH
1990
Rotational Resonance in a Spin-Lock Field for Solid State NMR
Gan, Z.H. and Grant, D.M.
Chemical Physics Letters, 168 (3,4), 1990. Funded by a National Institute of Health research grant from the Institution of General Medical Science.
In the magic angle spinning NMR experiment, a rotational resonance phenomenon occurs whenever a spin-lock rf field is either equal to or twice the sample spinning speed. The resonance occurs in the rotating frame where the spin-lock field assumes the role of the "Zeeman" interaction and the chemical shift modulated by the sample rotation is the "radio frequency" irradiation. The importance of good rf field homogeneity to the experiment is shown.
Molecular and Structural Information from Variable-Angle Spinning NMR Dipolar Spectra of C-13/N-14 Systems
Gan, Z.H. and Grant, D.M.
Journal of Magnetic Resonance, 1990 (In press). Funded by National Institute of Health.
A sample-spinning solid-state NMR study of a spin-1/2 nucleus coupled to a quadrupolar nucleus is presented. Using a simple approach, the quadrupolar effect is expanded in terms of irreducible spherical tensor components up to / = 4. Information on the electric field gradient tensor orientation, dipolar coupling, and chemical-shielding tensor for the C-13/N-14 system can be obtained experimentally from the magic-angle and the off-magic-angle sample-spinning spectra. Satisfactory results are obtained by comparing the simulations with the experimental spectra of tetramethylpyrazine, dimethyglyoxime, and triethylenediamine.
1988
The Effect of Transverse Cross Relaxation of NMR Dipolar Spectra
Gan, Z.H.; Facelli, J.C. and Grant, D.M.
Submitted to J. Chem. Phys., 1988. Funded by US Department of Energy.
The C-13 dipolar powder spectra of C-13H3P-31O(OH)2 at room temperature and C-13H3F-19 at low temperature (T=25K) are reported. An intense peak is observed in the center of the Pake doublet. This phenomenon is explained by the transverse cross relaxation mechanism between the C-13 and either the P-31 or F-19 nuclei. The chemical shielding tensors and dipolar coupling constants of these two molecules are obtained by fitting the experimental spectra.
C-13 Dipolar Spectroscopy of Nitromethane
Solum, M.S.; Facelli, J.C.; Gan, Z.H. and Grant, D.M.
Submitted to Molecular Physics, 1988. Funded by US Department of Energy.
The C-13 low temperature (25K) dipolar spectrum of C-13H3N-14O2 is reported. The spectrum was fit and the principal values of the C-13 shielding tensor are given. The C-13 shielding tensor principal values are similar to those found in other C-13H3 groups. Also, the N-14 quadrupolar parameters and the direct dipolar couplings were obtained from the fit. Because of librational motions an effective trace term in the dipolar interaction has to be included in the fit.