Scattering channel

Quack M 1985 On the densities and numbers of rovibronic states of a given symmetry species rigid and nonrigid molecules, transition states and scattering channels J. Chem. Phys. 82 3277-83... 

Even more remarkable, vibrational relaxation of NO(r = 15) on Au(lll) is characterized by profound multi-quantum vibrational relaxation. Specifically, the most probable vibrational scattering channel releases more than 150kJmol-1. Vibrational relaxation events exchanging as many as 10 vibrational quanta are observed. It appears likely that even more vibrational quanta can be exchanged with significant efficiency, but background problems prevented the observation of these channels. Thus the reported... 

Adjusting the gain on each of the scatter channels to ensure that single cells of interest are on scale. 

Several reasons have been put forward to explain the change in the angular intensity pattern of the photoelectrons. One explanation is that intermediate neutral energy levels are ac-Stark shifted into resonance and contribute new selection rules to the photoionization process [53,54], Another possibility is that the electrons of the Kr or D2 are driven into the core Kr+ or D2 in a scattering-like process that creates interference fringes in the photoelectron angular distribution due to interference between multiple scattering channels [55],... 

The total positron scattering cross section, erT, is the sum of the partial cross sections for all the scattering channels available to the projectile, which may include elastic scattering, positronium formation, excitation, ionization and positron-electron annihilation. Elastic scattering and annihilation are always possible, but the cross section for the latter process is typically 10-2O-10-22 cm2, so that its contribution to erT is negligible except in the limit of zero positron energy. All these processes are discussed in greater detail in Chapters 3-6. 

This is the optical theorem, and it expresses the conservation of the number of particles in the scattering process. As already mentioned in section 2.2, it is valid even when inelastic processes can occur, although dei is then replaced by the total scattering cross section [Pg.96]

The two sets of computations - forward scatter and side scatter - are made separately. In order to determine the complete size distribution, the forward and side scatter determinations must be combined. This is accomplished by adjusting the gain on the side scatter computations until those channels blend together with the distribution—incorporating both forward and side scatter distributions—is then renormalized and printed out as a l6-channel particle size distribution from 0.12 to 1 2.2 microns. Any Mie constant adjustment is made to the forward scatter computations alone because the side scatter channels are relatively insensitive to variations in the refractive index. 

We assume that Na atoms and Na2 molecules hitting the surface are either direcdy scattered back into the volume or are adsorbed, chemically equilibrated (2Na — Na2) at the surface and subsequently desorbed. We introduce the chemical accommodation coefficient p Ci) p is the probability that a wall collision proceeds through the reactive adsorption-desorption channel and 1 — p the probability that it proceeds through the non-reactive scattering channel, pj and P2, referring to incident Na atoms and Na2 molecules, respectively, are the free parameters of the model. Pi and P2 are assumed to be independent of surface temperature T, angle of incidence 0 and particle velocity v j,. The Na2 fraction of the particle flux (cm s ) desorbing from a surface element dSj at temperature Tj is qj, the Na fraction 1 — qj. In our model... 

A prerequisite which is at the heart of this nesting mechanism is the existence of a coherent Fermi liquid component in at least two spatial directions for temperatures below Actually, the possibility to single out the electron-hole scattering channel in the ladder summation rests on the existence of quasi-particles and a coherent 2D Fermi surface - in the same way as the electron-electron pairing channel is selected in the BCS theory of superconductors. Otherwise for T>t, the system is effectively ID in character and there is no possibility to select the electron-hole pairing channel. The electron system turns out not to be a Fermi liquid (see Section 4). 

The model is based at the outset from the observation that a ID non-interacting Fermi gas with a two-point Fermi surface at k° gives rise to two infrared logarithmic singularities in the response of the system to correlate pair of particles either in the electron-electron (Cooper) or in the 2k electron-hole (Peierls) scattering channel. These are of the form... 

The concept of the static dot is justified by the fact that the dot s translational and rotational degrees of freedom vary slowly as compared to the fast motion of the electrons. The parameters Edot and I of the scattering matrix S(E) represent adiabatic variables, validated by the Born-Oppenheimer approach. An instant conductivity of a movable dot is to be computed in a phase space of the NEM oscillator s coordinates x and momenta p. The x, p point plays the role of a partial scattering channel in which the Wigner delay time of electron tunneling r = dS (E) /dE is the shortest time scale. The marginal delay r... 

The number of scattering channels that partake in molecular reactions may increase very rapidly when chemical species or kinematical parameters are changed. For example rotational channels multiply as the moments of inertia of reactants or products decrease vibrational modes become numerous in polyatomic molecules and generally the number of accessible channels increases with increasing collision energies. In these cases it may not be possible, and sometimes it is not needed, to develop a detailed treatment of cross sections. Rather, one may want to know only averages of cross... 

Optical potentials have been used, so far, mostly to extract semi-empirical information from molecular beam experiments. In cases where detection devices are sensitive to only one type of species (or a single state), i.e. to only one reaction (or scattering) channel, the effect of competing reactions is to apparently decrease the detected scattering flux over the incoming one. This effect may be described in terms of optical or complex potentials... 

Molecular optical potentials for non-reactive processes may be rigorously defined by means of partitioning techniques (see e.g. Feshbach, 1962), which are based on the classification of scattering channels in two groups the first one includes states which are asymptotically selected or detected, and is characterized by a projection operator P the second one includes all other states (in practice those to which flux is lost) and is characterized by the projector Q. An optical potential operator VH may then be constructed as... 

Indeed, when the focus shifts to excited states, the formal and practical nature of fhe MEP changes, becoming more complicated theoretically and more demanding computationally. This statement is especially relevant to excited states that are found in the continuous spectrum and are unstable. Such unstable states ("resonances") decay into open scattering channels, with the continuum representing either free electrons (autoionization) or free atoms and ions (molecular autodissociation). 

The significance of the above statement must be understood in the context of possible problems involving a large variety of electronic structures and /or scattering channels that characterize the states of both the discrete and the continuous spectrum. 

The Rutherford back scattering/channeling (RBS/C) technique offers an unrivalled tool for a quantitative analysis of the amount of disorder created by ion irradiation. To measure the extent of the damage accumulation process, a commonly accepted parameter is the peak value of the... 

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