Ionization of atoms by charged particles

Ionization of hydrogen atom by charged particle impact are studied at different collisional energies and the total and differential cross sections are calculated. In case of light particle impact the final-state wave function here considers all three two-body interactions on an equal footing and satisfies the exact Coulomb boundary conditions. The spin asymmetries are also found and the values are compared with other existing results. For heavy particle impact a final continuum state wave function which incorporates distortion due to the Coulomb fields of both the projectile and the target nuclei is employed. In this case the target hydrogen atom is considered in its ground as well as metastable 2s state. The results thus obtained are compared with the existing experimental findings as well as other theoretical predictions.     

Inelastic scattering of charged particles by atoms using the Thomas-Fermi statistical method

We describe a method of calculating the differential cross section for the inelastic scattering of charged particles by atoms based on the statistical model of the atom. For the most general form of the potential of the atom we obtain an analytical expression for the differential (with respect to the energy of the electron ejected from the atom) cross section of inelastic scattering. It is shown that the statistical method of Thomas-Fermi is applicable when the energy of the ejected electron is sufficiently high.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 92–96, September, 1986.     

Scattering of atoms by light

This review discusses the latest theoretical and experimental achievements in the resonant light pressure acting on the translational motion of atoms. Alongside with the effects due to the spontaneous light pressure (atomic deflection, velocity bunching, cooling), various manifestations of the effects of induced light pressure are considered in detail. This paper provides the theory and experiments of atoms scattering by a standing light wave under the conditions of coherent and non-coherent interaction, diffraction and interference of atomic beams. The problems where atomic motion along two trajectories and Landau-Zener transitions between them are essential, are studied. The kinetic phenomena (scattering, cooling, channeling) due to the motion of the particles exposed to gradient force and also friction and diffusion caused by spontaneous emission are considered. The influence of the recoil effect under spontaneous emission of atoms on non-linear polarization phenomena is discussed.     

Scattering of electrons by atoms

The theoretical procedures of current interest in the calculation of electron atom scattering are discussed with emphasis on the intermediate energy range. The essential features of the mathematical methods are described. Some specific results are compared with experiment to illustrate the accomplishments and the limitations of the theory.     

Scattering states of charged particles in the ℤ2 gauge theoriesgauge theories

Scattering states of charged particles in a massive Euclidean lattice gauge model are constructed.Partially supported by CNPq     

Scattering of low-energy atoms by metallic surfaces

The problem of a neutral low-energy atom impinging on a well-defined metallic surface is approached from first principles. The solid and its potential energy of interaction with the incident atom is treated in the most general way, but under the following assumptions: (a) the conduction electrons interact adiabatically with the lattice ions and the gas atom; (b) no chemical reactions occur; (c) the one-phonon approximation is valid. The scattering amplitudes for surface and bulk mode excitations are obtained in terms of the dynamical properties of the metallic surface. Direct collisions of the incident atoms with the lattice ions are shown to give a negligible contribution to the scattering. The most important contribution comes from the interaction of the gas atom with the surface conduction electrons; the excitation of lattice vibrational modes occurs through the electron-phonon term of the Hamiltonian. The general expressions for the scattering amplitudes obtained show that the scattering is incoherent. With further assumptions one obtains a separation of the scattering amplitude into a coherent and incoherent part.     

A note on the projectile charge dependence of inner shell ionisation of atoms by heavy charged particles

The formula for the binding of the electron to the impinging projectile in inner shell ionization of atoms by heavy charged particles in the static approximation, are generalized to arbitrary electron wavefunctions. The effect is calculated for K-shell electrons using relativistic wavefunctions. A qualitative difference in the impact parameter dependency of the effect between light and heavy target are found.     

Scattering of partially polarized light by aligned atoms

A compact expression for the cross section of scattering of an arbitrarily polarized light by aligned atomic systems is obtained, in which the dependence on the geometric parameters and the Stokes parameters specifying the state of partial polarization of the incident radiation is represented in explicit form. The effect of atomic alignment and the processes of dissipation of the light energy on the polarization specific features and the angular distribution of the scattered light is investigated. In particular, it is shown that, if a dissipative channel is accessible, the angular distribution and the degree of linear polarization of scattered light depend on the degree of circular polarization of the incident radiation η₂. Dissipative processes also induce the circular polarization of the light scattered by aligned atoms when η₂=0.     

Scattering of protons and antiprotons by hydrogen atoms

The two-,four-,five-and fourteen-state approximations of the inpact parameter method have been applied to the excitation of hydrogen atoms by proton(p)and antiproton(p) impact.The effect of both channel and back couplings on the 2s and 2p excitations are investigated.The total cross sections are calculated for incident energies ranging from 1 to 2500keV.it is found that the effect of both channel and back couplings on the antiproton-induced reactions is greater than on that induced by protons.We compare the results with those of other theoretical and experimental works.     

Scattering by small thin dielectric particles

In the analysis of electromagnetic scattering by distributions of small dielectric particles an approximation to the scattered field can be obtained by representing the electrical interaction of the particles in terms of the dipole moments of the individual particles. The calculation of the moments necessitates the solution of certain static scattering problems, and this becomes numerically difficult when the particles are thin. An integral equation formulation of the static scattering problem specialized to the case of thin planar dielectric plates is presented, along with an efficient numerical routine. Dipole moments are obtained over a range of permittivities for plates with several thicknesses and a variety of cross-sectional shapes, and the shape dependence is discussed.     

Scattering of muonic hydrogen atoms

Our measurement compares the energy dependence of the scattering cross-sections of muonic deuterium and tritium on hydrogen molecules for collisions in the energy range 0.1–45 eV. A time-of-flight method was used to measure the scattering cross-section as a function of the muonic atom beam energy and shows clearly the Ramsauer–Townsend effect. The results are compared with theoretical calculations by using Monte Carlo simulations. The molecular pdμ and ptμ formation creates background processes. We measure the formation rates in solid hydrogen by detecting the 5.5 MeV (pdμ) and 19.8 MeV (ptμ) γ-rays emitted during the subsequent nuclear fusion processes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Scattering of electrons by charged dislocations in InSb-type semiconductors

Electron scattering by parallel arrays of charged dislocations in InSb-type semiconductors is considered. In the theoretical approach the nonparabolic structure of the conduction band of the semiconductors considered is taken into account in the approximation of a simplified Kane's band model. The effect of screening by free electrons of the dislocation charge is also included in the theory. The calculated relaxation time of the electrons is used to derive a formula for the dislocation-limited electron mobility in the semiconductors. Some examples of calculations of the charged dislocation-limited mobility as a function of the electron concentration with the dislocation density as a parameter are given for n-InSb at 77 K and 300 K. The ratio of the magnitudes of the charged dislocation-limited mobility to the ionized impurity-limited mobility in n-type material at low temperatures is also discussed.     

Scattering of particles by long-range magnetic fields

The seattering of nonrelativistic particles (either quantum mechanical or classical) by a magnetic field B is studied in any dimension ν ≥ 2. B(x) is allowed to decay like |x|^{−3.2 · δ} (δ > 0), as |x| → ∞. Assumptions are made about the field strengths and not about the potentials. A gauge is constructed for which the unmodified wave operators exist and are complete even though the corresponding classical motion need not be asymptotically free. The result also holds for Yang-Mills fields.     

Scattering of atoms and molecules by an electromagnetic field

The scattering of atoms and molecules by the force of stimulated light pressure appearing in a standing wave is considered. It is shown that short (10^-8s) light pulses of tunable lasers can deviate resonance atoms through an angle of about 5°. A high selectivity of scattering is retained in a standing wave even in conditions of great saturation. Therefore the considered effect can be used for the separation of isotopes.     

Trapping of charged particles by transverse electromagnetic waves

An estimate is made of the maximum number of resonant particles interacting with a transverse plane electromagnetic wave. This estimate is based on the distribution function, in terms of integrals characterizing the motion of particles in a wave. The values found here for proton fluxes accelerated by an amplitude-modulated wave in the solar corona agree with those measured during sporadic radioemission bursts.     

Structure functions and ionization of isolated atoms by charged projectiles

Inner-shell ionization of isolated atoms by incident charged particles is reexamined in the one-photon-exchange approximation. Within this framework we advocate the use of structure functions, which is popular in nuclear and particle physics. This method allows to obtain compact Lorentz- and gauge-invariant expressions. Projectiles of any spin and internal structure are easily accomodated in the formalism.K-shell ionization by relativistic electrons is calculated in a simple model.