Average‐Excitation‐Energy Approximation in the Calculation of Carbon‐13 Chemical Shifts of Nitrogen Heterocyclics

1969 ◽  
Vol 50 (2) ◽  
pp. 645-654 ◽  
Author(s):  
Waldemar Adam ◽  
Alec Grimison ◽  
Gladys Rodríguez
Keyword(s):  
Excitation Energy ◽  
Chemical Shifts ◽  
Energy Approximation ◽  
Average Excitation Energy

Zur theoretischen Interpretation der Anisotropie der 13C-NMR-chemischen Verschiebungen des Ethylens und Benzens auf halbempirischer Grundlage

1981 ◽  
Vol 36 (7) ◽  
pp. 763-767
Author(s):  
R. Radeglia
Keyword(s):  
Excitation Energy ◽  
Molecular Orbital ◽  
13C Nmr ◽  
Energy Method ◽  
Chemical Shifts ◽  
Average Energy ◽  
Localized Orbitals ◽  
Theoretical Interpretation ◽  
Molecular Plane ◽  
Average Excitation Energy

Abstract u r th e o re tis c h e n I n te r p r e ta t io n d e r A n is o tr o p ie d e r 13C -N M R -c h e m is d ie n V e rs c h ie b u n g e n des E th y le n s u n d B en zen s a u f h a lb e m p iris c h e r G r u n d la g e On the Semiempirical Theoretical Interpretation of the Anisotropy of 13C n.m.r. Chemical Shifts of Ethylene and Benzene The paramagnetic contribution of the 13C screening constants and their anisotropics are cal­ culated by using localized orbitals and the CNDO/2 method in the molecular orbital description. A comparison of the average energy method for calculating of shielding tensors with the sum-over-states method is performed. It is concluded that the average excitation energy is higher for the screening perpendicular to the molecular plane.

The stopping powers of atoms and molecules

1965 ◽  
Vol 285 (1402) ◽  
pp. 457-459 ◽  
Keyword(s):  
Excitation Energy ◽  
Charged Particles ◽  
Atoms And Molecules ◽  
Slowing Down ◽  
Average Excitation Energy

A procedure is described for calculating the average excitation energy of an atom or molecule appropriate to the slowing down of a beam of charged particles in a gas. The procedure is applied to helium with the result that its average excitation energy is 42∙0 eV.

Determining average excitation energy

1990 ◽  
Vol 242 (3-4) ◽  
pp. 309-312 ◽  
Author(s):  
William A. Friedman
Keyword(s):  
Excitation Energy ◽  
Average Excitation Energy

STUDY OF ANGULAR DISTRIBUTION OF HELIUM PROJECTILE FRAGMENTS IN INTERACTIONS OF 200 A GeV 32S IONS WITH EMULSION NUCLEI

1993 ◽  
Vol 08 (01) ◽  
pp. 21-31 ◽  
Author(s):  
◽  
M.I. ADAMOVICH ◽  
M.M. AGGARWAL ◽  
Y.A. ALEXANDROV ◽  
N.P. ANDREEVA ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Excitation Energy ◽  
High Precision ◽  
Minimum Bias ◽  
Single Source ◽  
Momentum Spread ◽  
Break Up ◽  
Average Excitation Energy ◽  
Bulk Part ◽  
Helium Emission

This paper presents data on the emission of helium fragments due to break up of 200 A GeV 32S ions in collision with emulsion nuclei. A total of 499 minimum bias events have been studied in an emulsion stack and 97 events in emulsion chambers. Emission angles of He fragments have been measured with high precision. This data has been compared with data of breakup of heavier as well as lighter projectiles and we observe that the value of the momentum spread, σ(p), increases with increasing projectile mass. The bulk part of the helium emission is consistent with a single source for helium fragments with an average excitation energy of (9.1±0.9) MeV. A tail of a few (<1%) He fragments with higher momenta is observed.

Résonance magnétique nucléaire 13C des dérivés allyliques de la colonne IV-A, de type (C6H5)3ECH2CH=CH—CH3. Effets électroniques du substituant du noyau aromatique

1984 ◽  
Vol 62 (1) ◽  
pp. 133-135 ◽  
Author(s):  
E. Matarasso-Tchiroukhine
Keyword(s):  
Excitation Energy ◽  
Electronic Excitation ◽  
Inductive Effect ◽  
Chemical Shifts ◽  
Aromatic Nucleus ◽  
Electronic Excitation Energy ◽  
Nmr Study ◽  
Résonance Magnétique ◽  
The Mean ◽  
C Nmr

The 13C nmr study of the series (C6H5)3ECH2CH=CH—CH31E shows, for the aromatic nucleus, a polarization consistent with a mesomeric electron withdrawing effect of the substituent in the case of E = Si, Ge, Sn; inversely, a mesomeric donating effect, in the case E = Pb, involving a higher electronegativity for Pb; and a donating π inductive effect, in the case E = C. The mean electronic excitation energy seems to dominate the chemical shifts of the aromatic carbons Cipso and Cortho, as well as the coupling 0J(13C—207Pb).

Proportionality relationships in the carbon-13 nuclear magnetic resonance spectra of para-disubstituted benzenes: a new interpretation of non-additive behavior

1977 ◽  
Vol 55 (3) ◽  
pp. 541-547 ◽  
Author(s):  
Brian Maurice Lynch
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Excitation Energy ◽  
Chemical Shifts ◽  
Correlation Coefficients ◽  
Energy Term ◽  
Nuclear Magnetic Resonance Spectra ◽  
New Interpretation ◽  
Parameter Approach

The carbon-13 chemical shifts for 214 distinct sites (the 4-carbons) in 24 sets of 1-X,4-Y-disubstituted benzenes and for 270 distinct sites (the 1- and 2-carbons) in 16 of these sets are reproduced with excellent precision (correlation coefficients 0.99 or greater) either by linear proportionality relationships with the appropriate substituent chemical shift (scs) in a mono-substituted benzene (for the 4-carbons), or by simple additivity relationships with the scs (for the 1- and 2-carbons).Inconsistencies are pointed out in a theoretical rationalization of 4-carbon shifts used in discussing the non-additivity of these shifts in terms of a DSP approach, whereas the above one-parameter approach yields sets of proportionality constants (slopes of scs relative to Y = H) following systematic trends which are interpreted as results of changes in the excitation energy term at carbon-4 dependent upon the ionization potential of the group Y. There is no significant association between the scs slopes and sets of calculated CNDO/2 electron densities for these para-disubstituted benzenes.

The chemical shift. I. Approximate theory and application to first row binary fluorides

1970 ◽  
Vol 48 (22) ◽  
pp. 3498-3503 ◽  
Author(s):  
F. G. Herring
Keyword(s):  
Perturbation Theory ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Average Energy ◽  
Approximate Theory ◽  
Hartree Fock ◽  
Nuclear Shielding ◽  
Energy Approximation

Starting from the approximations of the i.n.d.o.-l.c.a.o.-s.c.f. method and using approximate Hartree–Fock perturbation theory, a method has been developed whereby the nuclear shielding of a nucleus for a first row element may be estimated. The method avoids the use of the average energy approximation. The method is demonstrated by calculating the 19F chemical shifts in the first row binary fluorides relative to the fluorine molecule.

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