Photoelectron Spectra and Bonding in Some Halosilanes

1971 ◽  
Vol 49 (24) ◽  
pp. 4033-4046 ◽  
Author(s):  
D. C. Frost ◽  
F. G. Herring ◽  
A. Katrib ◽  
R. A. N. McLean ◽  
J. E. Drake ◽  
...  
Keyword(s):  
Bond Strength ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Ample Evidence ◽  
Carbon Compounds ◽  
Back Bonding ◽  
The Individual ◽  
D Orbitals

The photoelectron spectra of some halosilanes, SiH3X (X = F, Cl, Br), SiH2X2 (X = F, Cl), and SiHCl3 have been studied, to obtain information on the bonding, especially (p → d)π back-bonding to silicon. The spectra were assigned on simple orbital overlap grounds, by comparison with the carbon analogues and by use of CNDO/2 calculations. Few discrepancies were found, but in these cases the first method was preferred. There is ample evidence from the individual ionization potentials and by comparison of the spectra with those of the analogous carbon compounds for interaction of the halogen pπ electrons with the silicon d orbitals. This is also indicated by some empirical calculations on the chlorosilanes, which also confirm the assignment of the spectra.It can also be shown that the ionization potentials are consistent with the silicon–halogen σ bond strength decreasing through the series H3SiF > H3SiCl > H3SiBr.

The great Chinese surprise: the rupture with the United States is real and is happening

2020 ◽  
Vol 96 (2) ◽  
pp. 419-437
Author(s):  
Xiangfeng Yang
Keyword(s):  
United States ◽  
The United States ◽  
Donald Trump ◽  
Ample Evidence ◽  
Pendulum Swing ◽  
The Us ◽  
Methodological Problems ◽  
Trade War ◽  
The Stability ◽  
The Individual

Abstract Ample evidence exists that China was caught off guard by the Trump administration's onslaught of punishing acts—the trade war being a prime, but far from the only, example. This article, in addition to contextualizing their earlier optimism about the relations with the United States under President Trump, examines why Chinese leaders and analysts were surprised by the turn of events. It argues that three main factors contributed to the lapse of judgment. First, Chinese officials and analysts grossly misunderstood Donald Trump the individual. By overemphasizing his pragmatism while downplaying his unpredictability, they ended up underprepared for the policies he unleashed. Second, some ingrained Chinese beliefs, manifested in the analogies of the pendulum swing and the ‘bickering couple’, as well as the narrative of the ‘ballast’, lulled officials and scholars into undue optimism about the stability of the broader relationship. Third, analytical and methodological problems as well as political considerations prevented them from fully grasping the strategic shift against China in the US.

Photoelectron spectra and molecular properties. Scil2-ionization potentials and AB initio SCF calculations

1974 ◽  
Vol 26 (1) ◽  
pp. 20-24 ◽  
Author(s):  
B. Solouki ◽  
P. Rosmus ◽  
H. Bock
Keyword(s):  
Ab Initio ◽  
Molecular Properties ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Scf Calculations

A Discussion on photoelectron spectroscopy - Orderings of π and σ ionization potentials in carbocyclic and heterocyclic aromatic compounds

1970 ◽  
Vol 268 (1184) ◽  
pp. 131-140 ◽  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Aromatic Compounds ◽  
Lone Pair ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Light Sources ◽  
Orbital Energies ◽  
Substituted Pyridines ◽  
Nitrogen Lone Pair ◽  
Electron Correlation Effects

Data on calculated orbital energies and experimentally measured ionization potentials of carbocyclic and heterocyclic aromatic compounds are compared and contrasted. The ordering or orbital energies and ionization potentials do not always seem to parallel one another, probably owing to either electron correlation effects, or to deviations from Koopman’s theorem. The effects on photoelectron spectra of using different light sources and analysers are discussed in relation to their bearing on the orbital orderings of aromatic compounds. The high resolution He 584 A. photoelectron spectrum of pyridine is shown to be open to two interpretations regarding the ordering of the ionization potentials of the π orbitals and the ‘nitrogen lone pair’ (n). One of the interpretations involves the three lowest pyridine ionization potentials being π (9.2 eV), π L (9.5 eV) and n (10.5 eV) whilst the other has the first three ionization potentials being the order π , n, π . The photoelectron spectra of substituted pyridines and diazines are discussed in the light of the two possible explanations for the pyridine spectrum.

scholarly journals Disentangling age-dependent DNA methylation: deterministic, stochastic, and nonlinear

2020 ◽  
Author(s):  
O. Vershinina ◽  
M. Ivanchenko ◽  
M.G. Bacalini ◽  
A. Zaikin ◽  
C. Franceschi
Keyword(s):  
Dna Methylation ◽  
Environmental Factors ◽  
Methylation Level ◽  
Signal To Noise Ratio ◽  
Cross Sectional ◽  
Ample Evidence ◽  
Systematic Assessment ◽  
Relative Contribution ◽  
Age Dependent ◽  
The Individual

ABSTRACTDNA methylation variability arises due to concurrent genetic and environmental influences. Each of them is a mixture of regular and noisy sources, whose relative contribution has not been satisfactorily understood yet. We conduct a systematic assessment of the age-dependent methylation by the signal-to-noise ratio and identify a wealth of “deterministic” CpG probes (about 90%), whose methylation variability likely originates due to genetic and general environmental factors. The remaining 10% of “stochastic” CpG probes are arguably governed by the biological noise or incidental environmental factors. Investigating the mathematical functional relationship between methylation levels and variability, we find that in about 90% of the age-associated differentially methylated positions, the variability changes as the square of the methylation level, whereas in the most of the remaining cases the dependence is linear. Furthermore, we demonstrate that the methylation level itself in more than 15% cases varies nonlinearly with age (according to the power law), in contrast to the previously assumed linear changes. Our findings present ample evidence of the ubiquity of strong DNA methylation regulation, resulting in the individual age-dependent and nonlinear methylation trajectories, whose divergence explains the cross-sectional variability. It may also serve a basis for constructing novel nonlinear epigenetic clocks.

Photoelectron spectra of 3-substituted cyclopentenes. Correlations between ionization potentials and cycloaddition regioselectivity

1978 ◽  
Vol 100 (1) ◽  
pp. 105-110 ◽  
Author(s):  
E. J. McAlduff ◽  
Pierluigi Caramella ◽  
K. N. Houk
Keyword(s):  
Ionization Potentials ◽  
Photoelectron Spectra

Ionization potentials and intramolecular charge transfer. Photoelectron spectra of chloromethyl and methyl alkyl ethers

1986 ◽  
Vol 27 (2) ◽  
pp. 230-235
Author(s):  
V. V. Zverev ◽  
A. A. Bredikhin ◽  
V. M. Vakar' ◽  
A. N. Vereshchagin
Keyword(s):  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Alkyl Ethers

Photoelectron Spectrum and Electronic Structure of Tetrathiofulvalene (TTF)

1974 ◽  
Vol 52 (19) ◽  
pp. 3373-3377 ◽  
Author(s):  
A. John Berlinsky ◽  
James F. Carolan ◽  
Larry Weiler
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Molecular Orbital ◽  
Photoelectron Spectrum ◽  
Crystal Packing ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Molecular Orbital Calculations ◽  
Conducting Salt

The electronic structure of tetrathiofulvalene (TTF) has been determined from its photoelectron spectrum and the photoelectron data for the tetrahydro derivative of TTF and 1,3-dithiolane. Correlations of the ionization potentials (i.p.) and several molecular orbital calculations are used in the assignment of the photoelectron spectra of these three compounds. The first five i.p. of TTF and their assignment are as follows: 6.92 (3b1u), 8.67 (2b2g), 9.73 (2b1u), 10.16 (au) and 10.49 eV (b3g). The sixth i.p. at 11.00 eV is tentatively assigned to the 1b2g level. The electronic structure of TTF is important in understanding the crystal packing and band structure of the highly conducting salt, TTF•TCNQ.

The Photoelectron Spectra the Chloro Toluenes

1987 ◽  
Vol 40 (4) ◽  
pp. 751 ◽  
Author(s):  
JB Peel ◽  
EI Vonnagyfelsobuki
Keyword(s):  
Ab Initio ◽  
Cross Section ◽  
Valence Electron ◽  
Model Potential ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Molecule Model ◽  
Linear Correlations ◽  
Spectral Assignment

The HeI and HeII photoelectron spectra of the chloro toluenes have been measured. The spectra are assigned using HeI/HeII cross-section ratios and a composite-molecule model within an ab initio valence-electron-only model potential (VEOMP) framework. The order of the first two ionization potentials for the chloro toluenes is assigned as πS < πA which is contrary to the VEOMP assignment for benzal chloride and benzotrichloride , but is consistent with linear correlations using group electronegativities and σI scales. Furthermore, linear correlations using the first two ionization potentials of fluoro and chloro toluenes with group electronegativities are shown to be a useful aid in spectral assignment and, moreover, suggest that for benzyl fluoride and benzal chloride the most appropriate σI values are 0.20 and 0.31 respectively.

ChemInform Abstract: PHOTOELECTRON SPECTRA AND MOLECULAR PROPERTIES. LI. IONIZATION POTENTIALS OF SILANES SINH2N+2

1976 ◽  
Vol 7 (18) ◽  
pp. no-no
Author(s):  
H. BOCK ◽  
W. ENSSLIN ◽  
F. FEHER ◽  
R. FREUND
Keyword(s):  
Molecular Properties ◽  
Ionization Potentials ◽  
Photoelectron Spectra
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