Energy levels strained

Theoretical calculation at the HF/6-31G level99,102 on some S-S dications and their precursors have shown that the electronic structure of 1,4-dithionia-bicyclo[2.2.0]hexane and the sp-sp conformation of the tetramethyldisulfonium dication, the difference in the energy levels of [S] — [S] and [S] + n[S]103 is decreased owing to steric strain and the order of orbitals thus corresponds to case B. In the less strained systems (l,5-dithioniabicyclo[3.3.0]octane, 1,4-dithioniabicyclo[3.2.0]heptane), the order of orbitals corresponds to case C. Interestingly, ap-ap conformer of tetramethyldisulfonium dication was reported to correspond to case A. 

Hence, kinetic stability towards [4 + 2] dimerization increases from siloles to stannoles. Intracyclic bond lengthening (Si—C < Ge—C < Sn—C) must give rise to a decrease in the ring angular strain and to HOMO stabilization. This inhibits dimerization by an increase in the frontier orbital (HOMO/LUMO) energy-level difference. 

D is correct. Cycloheptane has the most ring strain and is at the greatest energy level. It will produce more heat per mole than methane or ethane because it is a larger molecule. 

The driving forces for electron transfer are a high-energy level of the highest occupied molecular orbital or a steric strain of the starting molecule. Complexation of oxygen by the electron-rich organic molecule has often been indicated as the first step of the mechanism. 

Ideally, lanthanide ions occupy site with C3V symmetry when incorporated into the GaN lattice by substituting the Ga3+. However the actual site symmetry is often found lower than C3V due to strain and defects. So far no crystal field analysis has ever been reported for lanthanide-doped III-V QDs, due to the co-existence of multi-sites which complicates the energy level structure and makes crystal field analysis difficult. Site selective spectroscopy is a very useful tool thus proposed to investigate the different crystal field environments of lanthanide ions doped in III-V QDs. 

LUMO energy and is the least reactive substrate while norbornene has the smallest HOMO-LUMO gap, the lowest LUMO energy and is the most reactive. They note that the LUMO energy level of an alkene is a useful approximation of its reactivity. They also note a correlation between a smaller C=C C bond angle and a lowering of the LUMO energy level - a link with Pericas theory of strain driving the reaction.12... 

There is much information that can be gained from the temperature dependent g values. The experimental data can be fitted to the vibronic energies and wavefunc-tions obtained from a parameterised Jahn-Teller surface with the low symmetry strain terms. The vibronic wavefunctions can then be used to calculate the g values and the energy levels can be used to determine the Boltzmann average. Implicit in this approach are the assumptions ... 

A stress applied to a crystal results in a strain. A phenomenological description of the electron energy levels under elastic strain was developed by Bardeen and Shockley [12]. It is referred to as the deformation potential approximation (DPA), in which the one-electron Hamiltonian is developed in a Taylor s series of the strain components The perturbation is written in cartesian coordinates, for a linear order in strain, as ... 

Porter [212] applied his group interaction modeling approach to both the nonlinear strain and the long-term mechanical properties of polymers. He showed that both problems can be explained qualitatively by his concept of discrete energy levels in a polymer. His key argument is that a fraction of rubberlike states coexists with the predominantly glassy state of a polymer below Tg is a function of the temperature, time and mechanical energy of deformation and... 

This method is based on measuring the shift of the optical energy levels of fluorescent elements such as Cr3+ in response to a change of the stress state. This results in undergo as the result of altering the distance of ions within the strained crystal structure of the host lattice (Yu and Clarke, 2002). Equipment used to record photoluminescence spectra include confocal laser-Raman spectrometers equipped with a liquid nitrogen cooled CCD detector and a motorised X-Y microscope table to allow point-by-point mapping. 

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