Simultaneous pair electronic

Any material which can form a color center contains two types of precursors as shown in Figure 2a. The hole center precursor is an atom, ion, molecule, impurity, or other defect which contains two paired electrons, one of which can be ejected by irradiation, leaving behind a hole center (Fig. 2b). The electron center precursor is an atom, ion, etc, which can produce an electron center by trapping the electron ejected from the hole center precursor. A hole and an electron center are thus formed simultaneously. Either or both can be the color center. Almost all materials have hole center precursors. If there is no electron center precursor, however, the displaced electron returns to its original place and the material remains unchanged. 

ELF can be visualized with different kinds of images. Colored sections through a molecule are popular, using white for high values of ELF, followed by yellow-red-violet-blue-dark blue for decreasing values simultaneously, the electron density can be depicted by the density of colored points. Contour lines can be used instead of the colors for black and white printing. Another possibility is to draw perspective images with iso surfaces, i.e. surfaces with a constant value of ELF. Fig. 10.2 shows iso surfaces with ELF = 0.8 for some molecules from experience a value of ELF = 0.8 is well suited to reveal the distribution of electron pairs in space. 

The resonance Raman enhancement profiles In Figures 7 and 8 show that the maximum Intensity of the Fe-O-Fe symmetric stretch falls to correspond to a distinct absorption maximum In the electronic spectrum. This Implies that the 0x0 Fe CT transitions responsible for resonance enhancement are obscured underneath other, more Intense bands. Although strong absorption bands In the 300-400 nm region (e > 6,000 M" cm"l) are a ubiquitous feature of Fe-O-Fe clusters, the Raman results make It unlikely that they are due to 0x0 -> Fe CT. An alternative possibility Is that they represent simultaneous pair excitations of LF transitions In both of the... 

The underlying joint atom-orbital probabilities, Pab(A,/),/ e B and Pab(B, /), / e A, to be used as weighting factors in the average conditional-entropy (covalency) and mutual-information (ionicity) descriptors of the AB chemical bond(s), indeed assume appreciable magnitudes only when the electron occupying the atomic orbital Xi of one atom is simultaneously found with a significant probability on the other atom, thus effectively excluding the contributions to the entropy/information bond descriptors due to the lone-pair electrons. Thus, such joint bond probabilities emphasize of AOs have both atoms are simultaneously involved in the occupied MOs. 

The reactions of butadiene, C4H6, with certain metal compounds are particularly interesting because bridged complexes are produced. This can occur because butadiene has two double bonds that can function simultaneously as electron pair donors to two metal atoms. When the reaction is carried out using CuCl and liquid butadiene at -10 °C, it can be represented by the following equation ... 

A detailed, simultaneous analysis (35) of the proton-decoupled 13C NMR spectrum and of the 13C satellites in the proton-decoupled 31P spectrum has allowed all the 31P-31P and 13C -31P coupling constants in 1,6-diphosphatriptycene to be evaluated (Table III). The large C(2)-P(l) coupling and small C(l)-P(6) coupling are considered to be strongly dependent on the orientation of the phosphorus lone-pair electrons and... 

Simultaneous pair transitions Simultaneous electronic transitions in two coupled absorbers or emitters. Because of the coupling, transitions which are spin-forbidden in one of the centres might become spin allowed (spin flip). 

Simultaneously, two electrons from the C=0 bond move onto the bottom oxygen atom to become a lone pair. 

COMPARISON OF THE ELECTRON PAIR AND MOLECULAR ORBITAL TREATMENTS The essential feature of the molecular orbital method is the complete freedom of movement of the electrons in the molecular orbitals. This means that one electron has no influence on the location of another electron and hence the probability of finding simultaneously one electron at a point 1, 1, -Cl and another at the point - 2 product of the... 

Fu et al. have developed a boron Lewis acid that bears both an empty a-symmetry orbital and an empty jr-symmetry orbital (Fig. 1) [162]. These vacant orbitals can simultaneously accept electron density from an oxygen lone pair and from the tt system of a carbonyl group. For instance, an X-ray diffraction study of air- and moisture-sensitive [( -borabenzene-THF)Cr(CO)3] reveals the THF binds to the boron atom... 

Fu and co-workers recently reported a new approach to restricting the rotational degree of freedom (see complex F), which focuses on the development of Lewis acids that bear an empty rr-symmetry and an empty 7t-symmetry orbital as illustrated in Fig. 1-8 [27]. These vacant orbitals can simultaneously accept electron from an oxygen lone pair and from the 7r-system of a carbonyl group. The distinguishing feature of this approach is the r-symmetry interaction, which at once organizes the Lewis acid-base complex and activates the carbonyl toward nucleophilic addition. 

The process, called pair production, involves a transformation of energy Into matter. A high-energy (>1.63x10 J) photon becomes an electron and a positron simultaneously. The electron and a proton in the nucleus form a neutron, while the positron is expelled. 

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