We have studied the angular time delay in slow-electron elastic scattering by spherical targets as well as the average time delay of electrons in this process. It is demonstrated how the angular time delay is connected to the Eisenbud–Wigner–Smith (EWS) time delay. The specific features of both angular and energy dependencies of these time delays are discussed in detail. The potentialities of the derived general formulas are illustrated by the numerical calculations of the time delays of slow electrons in the potential fields of both absolutely hard-sphere and delta-shell potential well of the same radius. The conducted studies shed more light on the specific features of these time delays.
We have studied the times delay of slow electrons scattered by a spherically symmetric rectangular potential well as functions of the well parameters. We have shown that the electron interaction with the scattering center qualitatively depends on the presence of discrete levels in the well. While electron retention dominates for the potential well with no discrete levels, the appearance of a level leads to the opposite situation where the incident electron hardly enters the scatterer. Such a behavior of the time delay is universal since we found it not only for the first s-level but also for the following arising s-, p-, and d-levels.
The Wigner time delay of slow particles in the process of their elastic scattering by complex targets formed by several zero-range potentials is investigated. It is shown that at asymptotically large distances from the target, the Huygens-Fresnel interference pattern formed by spherical waves emitted by each of the potentials is transformed into a system of spherical waves generated by the geometric center of the target. These functions determine flows of particles in and out through the surface of the sphere surrounding the target. The energy derivatives of phase shifts of these functions are the partial Wigner time delay.General formulas that connect the s-phase shifts of particle scattering by each of the zero-range potentials with the phases of particle scattering by the potential cluster forming the target are obtained. Model targets consisting of two-, three-and 4-centers are considered. It is assumed that these targets are built from identical delta-potentials with equal distances between their centers.The partial Wigner time delay of slow particles by considered targets are obtained. We apply the derived general formulas to consideration of electron scattering by atomic clusters that trap electron near the target, and by calculating the times delay of mesons scattered by few-nucleons systems.
Mass spectrometry of secondary ions represents a combination of analytical methods, which allows you to study the molecular characteristics of the solid state. On the basis of this method, the use of charged charging frequencies is directed at the power, usually in the range of tens of thousands of electron volts. Based on the molecular dynamics method, we simulated sputtering process in the form of water molecules and clusters of water films covering Au(111) on the surface at normal incidence. It is shown that the obtained mass spectra of sputtered particles contain peaks related to several water molecules. The analysis of the obtained results showed that peaks were formed on the mass spectrum of sputtered particles, which belong to water molecules, water clusters, and Au atoms. The results played a huge role in studying the surface of thin films and molecular spectroscopy. The obtained calculation results showed that the number of incident particles directly affects the sputtering process, that is, the greater the number of incident particles, the more intense the process of sputtering of the atoms of the upper layers of the substrate. This is due to the fact that the incident ions, destroying the structure of the crystal, namely, violating the periodicity of the upper atomic layers, remain in the substrate of the crystal.
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