Electron wave-length

Experimental Method.—The diffraction photographs were prepared with the apparatus and technique described by Brockway.3 Ten or more photographs were made for each substance, the electron wave length used being about 0.0613 A. and the camera distance 10.83 cm. The values of so = 4ir(sin 6/2)/X given in the tables are averages of the values found by visual measurement of ring diameters for ten or more films. 

A unique method for studying the phase composition and the atomic structure of crystalline materials. -> Electrodes and -> solid electrolytes are usually crystalline materials with a regular atomic structure that predicts their electrochemical behavior. For instance, the ionic transport in solid electrolytes or - insertion electrodes is possible only owing to the special atomic arrangement in these materials. The method is based on the X-ray (neutron or electron) reflection from the atomic planes. The reflection angle 9 depends on the X-ray (neutron or electron) wave length A and the distance d between the atomic planes (Braggs Law) ... 

It is of interest to note that the minimum electron wave length corresponding to this maximum energy is of the order of the distance between the atoms. 

X-ray Electromagnetic radiation of wave length c. 1 k. X-rays are generated in various ways, including the bombarding of solids with electrons, when they are emitted as a result of electron transitions in the inner orbits of the atoms bombarded. Each element has a characteristic X-ray spectrum. 

The electronic transitions which produce spectra in the visible and ultraviolet are accompanied by vibrational and rotational transitions. In the condensed state, however, rotation is hindered by solvent molecules, and stray electrical fields affect the vibrational frequencies. For these reasons, electronic bands are very broad. An electronic band is characterised by the wave length and moleculai extinction coefficient at the position of maximum intensity (Xma,. and emai.). 

ZINDO is an adaptation of INDO speciflcally for predicting electronic excitations. The proper acronym for ZINDO is INDO/S (spectroscopic INDO), but the ZINDO moniker is more commonly used. ZINDO has been fairly successful in modeling electronic excited states. Some of the codes incorporated in ZINDO include transition-dipole moment computation so that peak intensities as well as wave lengths can be computed. ZINDO generally does poorly for geometry optimization. 

Let us review the calculation of the number of electrons in successive Brillouin zones. The calculation has as its starting point a distribution of free electrons. In a volume V to which the electrons are restricted the most stable pair of electrons occupies the lowest energy levels, with nearly zero kinetic energy, and correspondingly long wave-lengths. As the number of electrons... 

The theoretically obtained electron densities of ions may be used for the calculation of the so-called F curves, which give the effective reflecting power of the ion as a function of the angle of reflection and the wave-length of X-rays, and which are of use in the determination of crystal structures. It may be mentioned that the high maximum value of the electron density at the nucleus given by our calculations provides considerable justification for the method of determining crystal structures with the aid of the relative intensities of Laue spots produced by crystal planes with complicated indices. 

The lowest excited state of azulene is predicted to possess 2 symmetry, which is in agreement with the result obtained using the symmetry rule. A recent vibrational analysis of the longest wave-length absorption band in the electronic spectrum of azulene indicates that the lowest-excited state would possess C2 symmetry . ... 

Fulvalene and heptafulvalene are predicted, in agreement with the result obtained using the symmetry rule, to suffer a symmetry reduction 2v in their lowest excited states. The longest wave-length electronic absorption bands of these molecules are expected to be relatively broad. This seems to be what is observed . On the other hand, the lowest excited state of sesquifulvalene is predicted not to undergo symmetry reduction, which again supports the prediction based on the symmetry rule. 

Chemically pure semiconducor materials can absorb only those photons, the energy hv of which exceeds the band gap E . Therefore, E. value determines the "red boundary of the light that is used in photocatalytic action of these materials. By way of example. Table 1 presents the values of Eg and the corresponding values of boundary wave length Xg= hc/E (where c is the velocity of light) for some semiconductor and dielectric oxides [2]. However, a semiconductor PC can be sensitized to light with X> by chemical modifications of its surface layer or adsorption of certain molecules on its surface, provided that such treatment creates additional full or empty electron levels in the band gap of the semiconductor material. 

In the cis form because of the proximity of two large benzene rings, they cannot be arranged in the same plane and there will be decreased overlap of the n electrons. This results in shorter wave lengths and lower extinction coefficient as composed with trans, which is planer, has larger Amax and extinction coefficient. So is also the case with cinnnamic acid where the values are ... 

An electron in the circle is called the excited electron. Absorption, although at a longer wave length than saturated hydrocarbons occurs below 9.4 x 101 K cal/mole. Therefore, ethers, disulphides, alkyl halides and alkyl amines are transparent to ultraviolet light. 

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