Collisions, elastic inelastic

Static defects scatter elastically the charge carriers. Electrons do not loose memory of the phase contained in their wave function and thus propagate through the sample in a coherent way. By contrast, electron-phonon or electron-electron collisions are inelastic and generally destroy the phase coherence. The resulting inelastic mean free path, Li , which is the distance that an electron travels between two inelastic collisions, is generally equal to the phase coherence length, the distance that an electron travels before its initial phase is destroyed ... 

We say such a collision is elastic if no energy transfers during the collision between the gas particle and the mirror but if energy does transfer - and it usually does - we say the collision is inelastic. 

Elastic-inelastic collision model, Szilard-Chalmers reaction and, 1 269 Electrical conduction, in organic superconductors, 29 278-286 Electrical conductivity of chalcogenide halide compounds, 23 331 of Group IB, 23 337-339, 342, 346-349 photoelectric effects, 23 368, 410 semiconductors, 23 368, 390, 395-396, 400-402, 410-412 superconductors, 23 375-377 of graphite intercalation compounds, 23 290, 294, 309-310, 312, 317-318 Electric discharges arc type, 6 146-147 chemical reactions in, 6 189-191 chemical reactions in, 6 143-206... 

Cross sections are defined for various kinds of collisions, such as elastic, inelastic, superelastic, reactive, etc. We are interested here mostly in the elastic collisions of atoms and molecules, often in the presence of light. If bulk properties are considered, averages of the cross sections over the velocity distribution are important the averaged cross sections become functions of temperature. 

Any solid material has its own upper limit of elastic deformation under either normal or tangential stresses. Once the stresses exceed this limit, plastic deformation will occur. In this section, collisions of inelastic spheres are presented. The degree of inelastic deformation is characterized by the restitution coefficient. 

After an energetic ion strikes a surface, it will decelerate as its kinetic energy is dissipated via elastic (nuclear collision) and inelastic processes. A small fraction of the ions may reflect from the surface the majority are implanted beneath the surface. The average distance an ion travels before it is stopped within a solid increases with collision energy. Figure 12 shows the mean depth of penetration achieved by He+ incident on a silicon surface. Molecular dynamics simulations reveal that within the first picosecond after a keV ion impacts a solid, a local hot spot develops at the... 

Gas-phase electron-transfer reactions have been studied using all the experimental methods which are of common use in the reaction dynamics community. These methods have been extensively described in the literature, and it is not necessary to describe them again in detail. We just need to recall a few points, which are necessary to understand the origin of the results discussed in the remainder of the chapter, and only the most recent and comprehensive reviews and a few original papers describing the principal techniques are referred to hereafter. It must be mentioned that the techniques used to study reactive collisions are in very wide use and have also been used to investigate non-reactive collisions, both inelastic and elastic. 

Elastic-collision model, Szilard-Chalmers reaction and, 268-269 Elastic-inelastic collision model, Szilard-Chalmers reaction and, 269 Electrolytes, sulfuric acid solutions, acids and, 400-403 acid-base reactions and, 403-405 anhydride formation and, 399 metal hydrogen sulfates and, 395-397 simple conjugate acid formation and, 397... 

For these inelastic particles it is required that the relative velocity component normal to the plane of contact, g2i k (before collision) and C21 k (after collision) satisfy the empirical relation (2.123) [31]. If the restitution coefficient therein is equal to one, the collision is elastic, which means that there is no energy loss during collision. Otherwise the collision is inelastic, which means that there is energy dissipation during collision. 

This interpretation of the electron response to the field disturbances is largely confirmed by the temporal course of the power gain from the field jn and power losses P" /n, and P /n in elastic, inelastic, and all collisions given in Fig. 18. For example, if the field pulse starts and ends with the low field (left), at the beginning of the pulse and in the later relaxation phase the power gain is almost compensated for by the power loss in elastic collisions, and this leads to the large relaxation time at these periods. However, around the pulse maximum, the power... 

Most collisions of the exciting radiation with molecules are elastic only about one in 10 collisions is inelastic. The incident energy that is scattered with no change in frequency elastically scattered) is called the Rayleigh line and it is much more intense than either Stokes or anti-Stokes lines. 

The concept of a potential energy surface, arising from the adiabatic approximation, is the basis of both the classical and quantum-mechanical treatment of the dynamics of elastic, inelastic and reactive collisions. The adiabatic potential energy V(x) governs the internal motions of atoms in an isolated system and determines the solutions of the nuclear wave equation (6.1) However, the results of a collision process will be entirely determined by the interaction potential V(x) only if the translation and rotation motion of the overall system do not influence its internal motions ... 

If the collision is non-reactive, the equation (73.Ill) holds at least before the collision. In the case of elastic collisions,it is valid also after the collision however, it is invalid when the collision is inelastic because of the conversion of translation into vibration energy after the moment of collision due to the curvature of the reaction coordinate. 

At low E/N, all internal and translational modes of both ions and gas molecules are equilibrated at T. Hence collisions, though inelastic individually, must be elastic on average (1.4.1). The internal modes of an ion and a molecule remain in equilibrium at their average translational ternperamres at any E/N, but at high E/N those temperatures (Tef and T, respectively) are unequal ions heat up and the gas does not. A miniscule firaction of ions in the IMS gas means a nil number of ion-molecule collisions compared to that of intermolecular ones, and all molecules... 

The two main sources of information about atomic and molecular structure and interatomic interactions are provided by spectroscopic measurements and by the investigation of elastic, inelastic, or reactive collision processes. For a long time these two branches of experimental research developed along separate lines without a strong mutual interaction. The main contributions of classical spectroscopy to the study of collision processes have been the investigations of collision-induced spectral line broadening and line shifts (Vol. 1, Sect. 3.3). 

Scattering of electrons, fast atoms, or ions with laser-excited atoms A can result in elastic, inelastic, or superelastic collisions. In the latter case, the excitation energy of A is partly converted into kinetic energy of the scattered particles. Orientation of the excited atoms by optical pumping with polarized lasers allows investigations of the influence of the atomic orientation on the differential cross sections for A + B collisions, which differs for collisions with electrons or ions from the case of neutral... 

Toennies JP. 1974. Molecular beam scattering experiments on elastic, inelastic, and reactive collisions . In Physical Chemistry, An Advanced Treatise, vol. VI A, lost W (ed.). Academic Press New York, NY 228-381. 

It is useful to classify the possible outcomes of collisions as elastic, inelastic, and reactive ... 

Although such systems have been extensively studied at higher collision energies over the last few deeades, the new experimental breakthroughs in creating dense samples of cold and ultracold molecules have provided unprecedented opportunities to explore elastic, inelastic, and reactive collisions at temperatures close to absolute zero. These studies have revealed unique aspects of molecular collisions and energy transfer mechanisms that are otherwise not evident in thermal energy collisions. 

Laser spectroscopy has contributed in an outstanding way to detailed studies of collision processes. Chapter 13 gives some examples of applications of lasers in investigations of elastic, inelastic, and reactive collisions. 

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