The chemical shift. II. A study of 14N chemical shifts in nitrogen–oxygen–halogen compounds

1970 ◽  
Vol 48 (22) ◽  
pp. 3504-3509 ◽  
Author(s):  
F. Aubke ◽  
F. G. Herring ◽  
A. M. Qureshi
Keyword(s):  
Angular Momentum ◽  
Chemical Shift ◽  
Excited States ◽  
Orbital Angular Momentum ◽  
Chemical Shifts ◽  
Hartree Fock ◽  
Halogen Compounds ◽  
Good Agreement

The chemical shifts of the 14N nucleus in a number of nitrogen–halogen–oxygen compounds have been estimated within the framework of the i.n.d.o.-l.c.a.o.-s.c.f. method using approximate perturbed Hartree–Fock theory. Generally good agreement with experiment is achieved. The calculations indicate that the variation in 14N chemical shift is due to either changes in orbital angular momentum, or to the presence of low lying excited states, or to a combination of both effects.

Microscopic description of the fusion excitation function of 32,36S+90,94,96Zr

2020 ◽  
Vol 29 (07) ◽  
pp. 2050046
Author(s):  
M. Rashdan ◽  
T. A. Abdel-Karim
Keyword(s):  
Excitation Function ◽  
Excited States ◽  
Density Functional ◽  
Neutron Density ◽  
Energy Density Functional ◽  
Hartree Fock ◽  
Density Distributions ◽  
Text Interaction ◽  
Good Agreement

The fusion excitation function for the systems [Formula: see text]S+[Formula: see text]Zr is investigated using a microscopic internuclear potential derived from Skyrme energy density functional. The inputs in this approach are the proton and neutron density distributions of the interacting nuclei, which are derived from Skyrme–Hartree–Fock calculations. The SkM[Formula: see text] interaction is used in the calculation of the nuclear densities as well as the internuclear potential. The coupling to low lying inelastic excited states of target and projectile is considered. The role of the neutron transfer is discussed, where it is considered through the CCFULL model calculation. A good agreement with the experimental data is obtained without adjustable parameters.

CORE LEVEL CHEMICAL SHIFTS AND LINE SHAPES FOR SYSTEMS WITH DIFFERENT VALENCIES AND Cu-O NETWORKS

2000 ◽  
Vol 14 (32) ◽  
pp. 3791-3830 ◽  
Author(s):  
K. KARLSSON ◽  
O. GUNNARSSON ◽  
O. JEPSEN
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Core Level ◽  
Photoemission Spectrum ◽  
Main Peak ◽  
Model Compounds ◽  
Line Shapes ◽  
Impurity Model ◽  
Anderson Impurity Model ◽  
Good Agreement

We have studied the Cu -2p core level photoemission spectrum of a variety of cuprates, mainly focusing on the chemical shift and the shape of the leading peak. The spectra are calculated using the Anderson impurity model and we obtain a very good agreement with the experimental data. We find that the shape of the leading peak depends crucially on the structure of the Cu - O network. The main peak turns out to be quite narrow if the network consists of Cu - O - Cu bond angels of the order of 90°. On the other hand, if the Cu - O atoms are arranged with bond angles of approximately 180°, the main peak becomes substantially broader and contains a rather complicated structure. However, in some cases it is not sufficient only to consider the Cu - O network because interactions with other atoms are also important. In the model compounds Cu 2 O , CuO and NaCuO 2, where Cu is formally monovalent, divalent and trivalent, respectively, we find that the number of 3d electrons is rather similar. Nevertheless, the binding energy increases with the valence as expected from chemical intuition. The spectra exhibit a large variation in the strength of the d9-like satellite and in the width of the main line. We, furthermore, study the chemical shift of three inequivalent Cu atoms in YBa 2 Cu 3 O 6.5, and compare the results with the model compounds, which suggests that the different Cu atoms in YBa 2 Cu 3 O 6.5 have formal valences of approximately one, two and three. These findings are analyzed and related to the formal valence.

SUBSTITUTIONAL AND CONFIGURATIONAL EFFECTS ON CHEMICAL SHIFT IN PYRANOID CARBOHYDRATE DERIVATIVES

1965 ◽  
Vol 43 (7) ◽  
pp. 2059-2070 ◽  
Author(s):  
R. U. Lemieux ◽  
J. D. Stevens
Keyword(s):  
Chemical Shift ◽  
Long Range ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Equatorial Orientation ◽  
Free Energies ◽  
Bonding Interaction ◽  
Conformational Properties ◽  
Good Agreement ◽  
Shielding Effects

The effects of long-range and virtual long-range coupling on the observed spectra of acetylated hexopyranoses and pentopyranoses are examined. Use is made of both spin decoupling and specific deuteration for the assignment of signals. It is seen that specific solvent effects on chemical shift can be superior to increasing the applied magnetic field for the resolution of the signals of closely related protons. The alteration of virtual long-range coupling effects in these ways can be useful in the diagnosis of spectra. Empirical rules are derived for estimating the long-range shielding effects which occur on changing configurations. It is seen that the inversion of a center can lead to deshielding of axial protons and to shielding of equatorial protons at other centers relative to the chemical shifts observed in reference compounds wherein all the acetoxy groups are in equatorial orientation. The effects in several cases result in equatorial protons giving their signal to higher field than chemically similar but axial protons. The conformational properties of pentopyranose tetraacetates as estimated from chemical shifts and coupling constants are seen to be in good agreement with expectations based on non-bonding interaction free energies. As expected, 2-deoxy-β-D-ribopyranose triacetate has the 1C-conformation when dissolved in chloroform.

HARTREE–FOCK WAVE FUNCTIONS FOR EXCITED STATES: III. DIPOLE TRANSITIONS IN THREE-ELECTRON SYSTEMS

1967 ◽  
Vol 45 (5) ◽  
pp. 1661-1673 ◽  
Author(s):  
Maurice Cohen ◽  
Paul S. Kelly
Keyword(s):  
Excited States ◽  
Wave Functions ◽  
Electron Systems ◽  
Matrix Elements ◽  
Isoelectronic Sequence ◽  
Hartree Fock ◽  
Transition Matrix Elements ◽  
Simplified Procedure ◽  
Good Agreement ◽  
Dipole Length

Hartree–Fock wave functions for a number of S, P, and D states of the lithium isoelectronic sequence have been calculated, using a simplified procedure described in an earlier paper. Transition matrix elements for all permitted dipole transitions between these states have been computed using both the dipole length and the dipole velocity formulations. The results are in good agreement with earlier calculations.

HARTREE–FOCK WAVE FUNCTIONS FOR EXCITED STATES: IV. OSCILLATOR STRENGTHS IN THE HELIUM ISOELECTRONIC SEQUENCE

1967 ◽  
Vol 45 (6) ◽  
pp. 2079-2090 ◽  
Author(s):  
Maurice Cohen ◽  
Paul S. Kelly
Keyword(s):  
Matrix Element ◽  
Excited States ◽  
Transition Matrix ◽  
Transition Matrix Element ◽  
Wave Functions ◽  
Oscillator Strengths ◽  
Isoelectronic Sequence ◽  
Hartree Fock ◽  
Good Agreement

Orbital wave functions for a number of singlet and triplet S, P, and D states of the helium sequence through C+4 have been calculated using an approximation described earlier. The wave functions have been employed to calculate the oscillator strengths for all allowed dipole transitions between these states, using both the length and velocity forms of the transition matrix element. Our results are in good agreement with the most accurate values available.

scholarly journals Detection of methylation, acetylation and glycosylation of protein residues by monitoring 13C chemical-shift changes

2016 ◽  
Author(s):  
Pablo G. Garay ◽  
Osvaldo A. Martin ◽  
Harold A. Scheraga ◽  
Jorge A. Vila
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Biological Processes ◽  
Proof Of Concept ◽  
Post Translational Modifications ◽  
13C Chemical Shifts ◽  
Protein Residues ◽  
Lysine Residues ◽  
13C Chemical Shift ◽  
Good Agreement

Post-translational modifications of proteins expand the diversity of the proteome by several orders of magnitude and have a profound effect on several biological processes. Their detection by experimental methods is not free of limitations such as the amount of sample needed or the use of destructive procedures to obtain the sample. Certainly, new approaches are needed and, therefore, we explore here, as a proof-of-concept, the feasibility of using 13C chemical shifts of different nuclei to detect methylation, acetylation and glycosylation of protein residues by monitoring the deviation of the 13C chemical shifts from the expected (mean) experimental value of the non-modified residue. As a validation test of this approach, we compare our theoretical computations of the 13Ce chemical-shift values against experimental data, obtained from NMR spectroscopy, for methylated and acetylated lysine residues with good agreement within ~1 ppm. Then, further use of this approach to select the most suitable 13C-nucleus, with which to determine other modifications commonly seen, such as methylation of arginine and glycosylation of serine, asparagine and threonine, shows encouraging results.

scholarly journals Controlling Conical Beam Carrying Orbital Angular Momentum with Transmissive Metasurface

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jun Sun ◽  
Ke Chen ◽  
Kai Qu ◽  
Junming Zhao ◽  
Tian Jiang ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
High Speed ◽  
Design Method ◽  
Cone Angle ◽  
Full Control ◽  
Potential Applications ◽  
Conical Radiation ◽  
Conical Beam ◽  
Good Agreement

Conical beams have potential uses in wireless and satellite-based communication. In this study, we propose a method using a transmissive metasurface to achieve full control of the diverging effect of orbital angular momentum (OAM) modes to form the desired conical beam. A patch antenna functioning as the feed source is combined with the transmissive metasurface to enable the integration of the source and metasurface. For full control of conical radiation, including the cone angle and OAM mode, we introduce both radial and circumferential phase gradients to the proposed metasurface. Experiments are conducted in the microwave region to validate the design method, which shows good agreement with the simulation results. The proposed metasurface provides a means of flexibly generating conical beams with the designed OAM mode to assist potential applications in high-speed wireless communication.

A 139La NMR study of the interactions between the La(III) cation and D-ribose in aqueous solution

1994 ◽  
Vol 72 (7) ◽  
pp. 1753-1757 ◽  
Author(s):  
Zhigang Chen ◽  
Nicole Morel-Desrosiers ◽  
Jean-Pierre Morel ◽  
Christian Detellier
Keyword(s):  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Stability Constant ◽  
Chemical Shifts ◽  
Similar Treatment ◽  
Calorimetric Measurements ◽  
Nmr Study ◽  
The Stability ◽  
Good Agreement

The interactions of the La(III) cation with D-ribose and with D-arabinose in aqueous solution were investigated by 139La NMR spectroscopy. In the case of D-ribose, the formation of a La(III)-sugar complex was indicated by variations of the 139La chemical shift and linewidth with an increase of the sugar concentration in solution. In contrast, the complexation of La(III) by arabinose is very weak and almost undetectable by 139La NMR. On the basis of a 1:1 stoichiometry, the stability constant for the complex of La(III) with D-ribose was calculated from the observed 139La chemical shift values. A similar treatment was done for the viscosity corrected 139La linewidths using arabinose as an uninteractive reference. The stability constants, K, obtained independently from 139La chemical shifts and linewidths are in good agreement, 2.8 ± 0.5 and 2.2 ± 0.6 M−1 respectively at 299.0 ± 0.5 K. The thermodynamic parameters for the complexation of La(III) by D-ribose could also be obtained: ΔH0 = −12 ± 2 kJ mol−1, and ΔS0 = −31 ± 5 J K−1 mol−1. These values are in very good agreement with those obtained by calorimetric measurements.

scholarly journals Mass formula for light nonstrange mesons and Regge trajectories in quark model

2017 ◽  
Vol 32 (25) ◽  
pp. 1750153 ◽  
Author(s):  
Duojie Jia ◽  
Cheng-Qun Pang ◽  
Atsushi Hosaka
Keyword(s):  
Experimental Data ◽  
Angular Momentum ◽  
Quark Model ◽  
Excited States ◽  
Orbital Angular Momentum ◽  
Mass Formula ◽  
Field Method ◽  
Auxiliary Field ◽  
Regge Trajectories ◽  
Light Mesons

We study the Regge-like spectra of light mesons in a relativized quark model. An analytical mass formula is presented for the light unflavored mesons with the help of auxiliary field method, by which a quasi-linear Regge–Chew–Frautschi plot is predicted for the orbitally excited states. We show that the trajectory slope is proportional to the inverse of the confining parameter [Formula: see text] when the orbital angular momentum [Formula: see text] is large. The result is tested against the experimental data of the spectra of the meson families [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] in the [Formula: see text] planes, with the fitted parameters consistent with that in the literatures.

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