17O N.M.R. Line Broadening and T1, T2 Measurements on CrO42- and HCrO4-

1996 ◽  
Vol 49 (6) ◽  
pp. 697 ◽  
Author(s):  
NE Brasch ◽  
DA Buckingham ◽  
CR Clark ◽  
AE Rowan
Keyword(s):  
Line Width ◽  
Spin Exchange ◽  
Spin Coupling ◽  
Line Broadening ◽  
Rapid Exchange ◽  
Exchange Effects ◽  
T1 And T2 ◽  
The Difference

The increase in the line width of the 17O signal of CrO42- (ΔvCrO42- = 11�2 Hz) on adding acid is attributed to a much broader HCrO4- signal ΔvHCrO4). This broadening is shown to have acid-independent (Δv0 = 67�5 Hz) and acid-dependent [Δv1 = (1.0�0.1) × 108 Hz M-1] contributions. Direct T1 and T2 measurements give T1 ≈ 70 ms, T2 ≈ 40 ms for CrO42- with the difference being attributed to spin coupling (T2' = 90 ms). For HCrO4- T1 = 8�3 ms, and the acid- catalysed Δv1 contribution is attributed to rapid exchange of H,+ in H2CrO4 (k ≈ 1×109 s-1) showing that spin exchange effects are important for this ion.

Excitation of transitions between atomic or molecular energy levels by monochromatic laser radiation - II. Excitation under conditions of strictly inhomogeneous line broadening and mixed homogeneous and inhomogeneous broadening

1978 ◽  
Vol 362 (1708) ◽  
pp. 13-25 ◽  
Keyword(s):  
Laser Radiation ◽  
Line Width ◽  
Energy Levels ◽  
Incident Radiation ◽  
Exciting Radiation ◽  
Half Line ◽  
Line Broadening ◽  
Moment Matrix ◽  
Inhomogeneous Line Broadening ◽  
Inhomogeneous Line

The development with time of the excitation of a transition between two atomic or molecular energy levels under the influence of monochromatic laser radiation is examined under conditions of strictly inhomogeneous line broadening due to such causes as doppler shift arising from translational velocity. The ratio of the number of molecules, N 2 , in an excited state to the total number, N , is calculated for various ratios of the intensity parameter β ═ E 0 μ / ħ to the half line-width ∆ , where E 0 is the amplitude of the electric field in the incident radiation and is the dipole moment matrix element for the transition. Excitation functions obtained in a previous paper (I) for various values of the ratio γ/β , where γ is the half line-width in the absence of inhomo­geneous broadening, are used to obtain the variation of N 2 / N with time under conditions of mixed broadening for various values of the ratio γ/∆ and γ/β , when the exciting radiation is in exact resonance with the central frequency of the transition.

scholarly journals Origin of the residual line width under frequency-switched Lee–Goldburg decoupling in MAS solid-state NMR

2020 ◽  
Vol 1 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Johannes Hellwagner ◽  
Liam Grunwald ◽  
Manuel Ochsner ◽  
Daniel Zindel ◽  
Beat H. Meier ◽  
...  
Keyword(s):  
Solid State ◽  
Line Width ◽  
Floquet Theory ◽  
Pulse Sequence ◽  
Second Order ◽  
Magic Angle ◽  
Line Broadening ◽  
Third Order ◽  
Order Error ◽  
Error Terms

Abstract. Homonuclear decoupling sequences in solid-state nuclear magnetic resonance (NMR) under magic-angle spinning (MAS) show experimentally significantly larger residual line width than expected from Floquet theory to second order. We present an in-depth theoretical and experimental analysis of the origin of the residual line width under decoupling based on frequency-switched Lee–Goldburg (FSLG) sequences. We analyze the effect of experimental pulse-shape errors (e.g., pulse transients and B1-field inhomogeneities) and use a Floquet-theory-based description of higher-order error terms that arise from the interference between the MAS rotation and the pulse sequence. It is shown that the magnitude of the third-order auto term of a single homo- or heteronuclear coupled spin pair is important and leads to significant line broadening under FSLG decoupling. Furthermore, we show the dependence of these third-order error terms on the angle of the effective field with the B0 field. An analysis of second-order cross terms is presented that shows that the influence of three-spin terms is small since they are averaged by the pulse sequence. The importance of the inhomogeneity of the radio-frequency (rf) field is discussed and shown to be the main source of residual line broadening while pulse transients do not seem to play an important role. Experimentally, the influence of the combination of these error terms is shown by using restricted samples and pulse-transient compensation. The results show that all terms are additive but the major contribution to the residual line width comes from the rf-field inhomogeneity for the standard implementation of FSLG sequences, which is significant even for samples with a restricted volume.

scholarly journals Residual dipolar line width in magic-angle spinning proton solid-state NMR

2021 ◽  
Vol 2 (1) ◽  
pp. 499-509
Author(s):  
Matías Chávez ◽  
Thomas Wiegand ◽  
Alexander A. Malär ◽  
Beat H. Meier ◽  
Matthias Ernst
Keyword(s):  
Chemical Shift ◽  
Line Width ◽  
Magic Angle Spinning ◽  
Spin Systems ◽  
Second Order ◽  
Magic Angle ◽  
Line Broadening ◽  
Third Order ◽  
Angle Spinning ◽  
Effective Hamiltonians

Abstract. Magic-angle spinning is routinely used to average anisotropic interactions in solid-state nuclear magnetic resonance (NMR). Due to the fact that the homonuclear dipolar Hamiltonian of a strongly coupled spin system does not commute with itself at different time points during the rotation, second-order and higher-order terms lead to a residual dipolar line broadening in the observed resonances. Additional truncation of the residual broadening due to isotropic chemical-shift differences can be observed. We analyze the residual line broadening in coupled proton spin systems based on theoretical calculations of effective Hamiltonians up to third order using Floquet theory and compare these results to numerically obtained effective Hamiltonians in small spin systems. We show that at spinning frequencies beyond 75 kHz, second-order terms dominate the residual line width, leading to a 1/ωr dependence of the second moment which we use to characterize the line width. However, chemical-shift truncation leads to a partial ωr-2 dependence of the line width which looks as if third-order effective Hamiltonian terms are contributing significantly. At slower spinning frequencies, cross terms between the chemical shift and the dipolar coupling can contribute in third-order effective Hamiltonians. We show that second-order contributions not only broaden the line, but also lead to a shift of the center of gravity of the line. Experimental data reveal such spinning-frequency-dependent line shifts in proton spectra in model substances that can be explained by line shifts induced by the second-order dipolar Hamiltonian.

scholarly journals Variability in Thyroid Cancer Multidisciplinary Team Meeting Recommendations Is Not Explained by Standard Variables: Outcomes of a Single Centre Review

2021 ◽  
Vol 10 (18) ◽  
pp. 4150
Author(s):  
Mark E. Fenton ◽  
Sarah A. Wade ◽  
Bibi N. Pirrili ◽  
Zsolt J. Balogh ◽  
Christopher W. Rowe ◽  
...  
Keyword(s):  
Decision Making ◽  
Total Thyroidectomy ◽  
Multidisciplinary Team ◽  
Univariate Analysis ◽  
Decision Making Process ◽  
Completion Thyroidectomy ◽  
Measured Variable ◽  
T1 And T2 ◽  
The Difference ◽  
Therapeutic Decision Making

Multidisciplinary team (MDT) meetings are the mainstay of the decision-making process for patients presenting with complex clinical problems such as papillary thyroid carcinoma (PTC). Adherence to guidelines by MDTs has been extensively investigated; however, scarce evidence exists on MDT performance and variability where guidelines are less prescriptive. We evaluated the consistency of MDT management recommendations for T1 and T2 PTC patients and explored key variables that may influence therapeutic decision making. A retrospective review of the prospective database of all T1 and T2 PTC patients discussed by the MDT was conducted between January 2016 and May 2021. Univariate analysis (with Bonferroni correction significance calculated at p < 0.006) was performed to establish clinical variables linked to completion thyroidectomy and Radioactive iodine (RAI) recommendations. Of 468 patients presented at thyroid MDT, 144 pT1 PTC and 118 pT2 PTC met the selection criteria. Only 18% (n = 12) of pT1 PTC patients initially managed with hemithyroidectomy were recommended completion thyroidectomy. Mean tumour diameter was the only variable differing between groups (p = 0.003). pT2 patients were recommended completion thyroidectomy in 66% (n = 16) of instances. No measured variable explained the difference in recommendation. pT1 patients initially managed with total thyroidectomy were not recommended RAI in 71% (n = 55) of cases with T1a status (p = 0.001) and diameter (p = 0.001) as statistically different variables. For pT2 patients, 60% (n = 41) were recommended RAI post-total thyroidectomy, with no differences observed among groups. The majority of MDT recommendations were concordant for patients with similar measurable characteristics. Discordant recommendations for a small group of patients were not explained by measured variables and may have been accounted for by individual patient factors. Further research into the MDT decision-making process is warranted.

Spin Exchange Effects in Ferromagnetic Resonance

1956 ◽  
Vol 103 (2) ◽  
pp. 280-286 ◽  
Author(s):  
James Ross Macdonald
Keyword(s):  
Ferromagnetic Resonance ◽  
Spin Exchange ◽  
Exchange Effects

31P-NMR spectroscopy of isolated perfused rat lung

1993 ◽  
Vol 74 (4) ◽  
pp. 1549-1554 ◽  
Author(s):  
Y. Hayashi ◽  
T. Inubushi ◽  
S. Nioka ◽  
R. E. Forster
Keyword(s):  
Nmr Spectroscopy ◽  
Intracellular Ph ◽  
31P Nmr ◽  
Peak Height ◽  
31P Nmr Spectroscopy ◽  
Line Broadening ◽  
Membrane Phospholipids ◽  
The Difference ◽  
Inflated Lung

We obtained 202.5-MHz 31P-nuclear magnetic resonance (NMR) spectra of isolated perfused rat lungs, degassed and inflated, and of lung extract. The spectra included those of ATP, ADP, phosphocreatine (PCr), inorganic phosphate (Pi), phosphomonoesters, phosphodiesters, and a broad component due to the membrane phospholipids. The line width at one-half peak height for beta-ATP was 1.0 ppm for the degassed lung and 1.2 ppm for the inflated lung. This suggests that the air-water interfaces in inflated lung, which produce proton NMR line broadening, do not act prominently in 31P-NMR spectroscopy. In a degassed lung, when perfusion was stopped for up to 30 min, PCr and ATP peaks decreased progressively with time while Pi and phosphomonoester peaks increased. On return of flow, these changes reversed. The intracellular pH values calculated from the difference in magnetic field between PCr and Pi peaks of inflated and degassed lungs were 7.16 +/- 0.10 (SD; n = 4) and 6.99 +/- 0.10 (n = 4), respectively. The change of intracellular pH caused by 30 min of ischemia was -0.2 pH units. Our findings indicate that air-water interfaces should not broaden lung 31P peaks in vivo.

scholarly journals Spin-exchange effects in elastic electron scattering from linear triatomic radicals

2010 ◽  
Vol 21 (2) ◽  
pp. 226-233
Author(s):  
M. M. Fujimoto ◽  
S. E. Michelin ◽  
F. Arretche ◽  
K.T. Mazon ◽  
M.-T. Lee ◽  
...  
Keyword(s):  
Electron Scattering ◽  
Spin Exchange ◽  
Elastic Electron ◽  
Elastic Electron Scattering ◽  
Exchange Effects ◽  
Triatomic Radicals

Spin exchange effects in radical pair CIDEP ag

1984 ◽  
Vol 110 (3) ◽  
pp. 280-284 ◽  
Author(s):  
A.I. Grant ◽  
N.J.B. Green ◽  
P.J. Hore ◽  
K.A. McLauchlan
Keyword(s):  
Spin Exchange ◽  
Radical Pair ◽  
Exchange Effects

Probing of the Wave Function of Shallow Donors and Acceptors by EPR in SiC Crystals with Changed Isotopic Composition

2005 ◽  
Vol 483-485 ◽  
pp. 507-510
Author(s):  
Marina V. Muzafarova ◽  
Ivan V. Ilyin ◽  
E.N. Mokhov ◽  
P.G. Baranov ◽  
B.Ya. Ber ◽  
...  
Keyword(s):  
Wave Function ◽  
Band Structure ◽  
Isotopic Composition ◽  
Density Distribution ◽  
Spin Density ◽  
Main Part ◽  
Shallow Donor ◽  
Line Broadening ◽  
Electronic Wave Function ◽  
The Difference

The conclusion which is drawn from the EPR line broadening and narrowing of the N shallow donor in an isotope enriched and non-enriched 4H-SiC and 6H-SiC crystals along with previous ENDOR results shows that the spin-density distribution over the C and Si nuclei differs between the 4H-SiC and 6H-SiC polytypes. The main part of the spin density in 4H-SiC is located on the Si sublattice. In contrast, in 6H-SiC the main part of the spin density is located on the C sublattice. An explanation for the difference in the electronic wave function of the N donor in 4HSiC and 6H-SiC can be found in the large difference in the band structure of two polytypes and in the position of the minima in the Brillouin zone.

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