Determination of Nuclear Quadrupole Coupling Constants from Nuclear Magnetic Resonances in Polycrystalline Solids

1964 ◽  
Vol 40 (1) ◽  
pp. 149-152 ◽  
Author(s):  
P. A. Casabella
Keyword(s):  
Coupling Constants ◽  
Quadrupole Coupling ◽  
Polycrystalline Solids ◽  
Nuclear Quadrupole ◽  
Magnetic Resonances ◽  
Nuclear Magnetic

Determination of the Sign of Nuclear Quadrupole Interaction by Laser-Radiofrequency Double-Resonance Determination of the Sign of Nuclear Quadrupole Interaction by Laser-Radiofrequency Double-Resonance

1994 ◽  
Vol 49 (1-2) ◽  
pp. 14-18
Author(s):  
Tilo Blasberg ◽  
Dieter Suter
Keyword(s):  
Quadrupole Interaction ◽  
Double Resonance ◽  
High Sensitivity ◽  
Quadrupole Coupling Constant ◽  
Nuclear Quadrupole Interaction ◽  
Coupling Constants ◽  
Quadrupole Coupling ◽  
New Type ◽  
Nuclear Quadrupole

Abstract We describe a new type of laser-radiofrequency double-resonance experiment, which allows to determine not only the absolute value but also the sign of nuclear quadrupole coupling constants. This determination of the sign, which is essential for the comparison with calculated EFG tensors, is not possible with purely magnetic experiments. The m ethod has a high resolution and, because of the optical detection, also a high sensitivity. As an example, the quadrupole coupling constant for Pr3+ :YAlO3 was measured at 4.38 K and was found to be negative.

Quadrupoleffekte der magnetischen Kernresonanz an 11B in Bor-Stickstoffverbindungen

1969 ◽  
Vol 24 (4) ◽  
pp. 566-572 ◽  
Author(s):  
Klaus Wiedemann ◽  
Jürgen Voitländer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Quadrupole Interaction ◽  
Second Order ◽  
Coupling Constants ◽  
Quadrupole Coupling ◽  
Wide Line ◽  
Nuclear Quadrupole ◽  
Asymmetry Parameters ◽  
Nuclear Magnetic

Abstract First and second-order quadrupole effects of the 11B nuclear magnetic resonance have been measured in polycrystalline samples of dimere dimethylaminoboranes and tetramethylboracene. With the theory of powder patterns for first and second-order quadrupole interaction the nuclear quadrupole coupling constants e2 q Q/h and asymmetry parameters η of 11B have been determined. For these measurements boron-free inserts had to be constructed for the probes of the Varian Wide Line Spectrometer DA 60.

Halogen Nuclear Quadrupole Coupling Constants in Non-axially symmetric Molecules; Ab initio Calculations, which Include Correlation, Compared with Experiment

1998 ◽  
Vol 53 (6-7) ◽  
pp. 370-382
Author(s):  
Michael H. Palmer ◽  
John A. Blair-Fish
Keyword(s):  
Ab Initio ◽  
Relativistic Effects ◽  
Close Correlation ◽  
Equilibrium Structure ◽  
Cylindrical Symmetry ◽  
Coupling Constants ◽  
Axially Symmetric ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Abstract Ab initio determination of the electric field gradient (EFG) tensors at halogen and other centres ena-bled determination of the nuclear quadrupole coupling constants (NQCC) for a diverse set of C2v , C3v and other symmetry molecules of general formula MH2X2 and MHX3 , where the halogen atoms (X) are Cl, Br and I, and the heavy central atoms (M) are C and Si. The study presents results at a standardised level of calculation, triple-zeta in the valence space plus polarisation functions (TZVP) for the equilib-rium geometry stage; all-electron MP2 correlation is included in all these studies. For the bromo and iodo compounds, especially the latter, it is essential to allow core polarisation, by decontraction of the p,d-functions. This is conveniently done by initial optimization of the structure with a partly contract-ed basis, followed by reestablishment of the equilibrium structure with the decontracted basis.The NQCCs, derived from the EFGs, using the 'best' values for the atomic quadruple moments Cl, Br and I, lead to good agreement with the inertial axis (IA) data obtained from microwave spectroscopy. When the data from the present study is plotted against the values derived from the IA data, obtained by whatever approximations chosen by the MW authors, we obtain a linear regression for the data (85 points) with the slope 1.0365 and intercept -0.1737, with standard errors of 0.0042 and 0.2042, respectively; these are statistically identical results irrespective of whether the data is restricted to IA or EFG principal axis (PA) data.Since as in the C3v MH3X compounds studied previously, a close correlation of the microwave spectral data with the calculations was observed using the 'best' current values for Qz , there seems no need to postulate that the values of QBr for both 79Br and 81Br are seriously in error. A scaling downwards of Qz by about 5% for Br and I increases the agreement with experiment, but the contributions of relativistic effects are unknown, and could lead to further reassessment.Of the two common assumptions used in MW spectroscopy, to convert from IA to EFG-PA data, either (a) cylindrical symmetry of the NQCC along the bond direction, or (b) coincidence of the tensor principal element with the bond axis, the latter is found to be a much more realistic approximation.

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