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© 2018 Elsevier B.V. The non-Markovian dynamics of a charged particle linearly coupled to a neutral bosonic heat bath is investigated in an external uniform magnetic field. The analytical expressions for the time-dependent and asymptotic friction and diffusion coefficients, cyclotron frequencies, variances of the coordinate and momentum, and orbital magnetic moments are derived. The role of magnetic field in the dissipation and diffusion processes is illustrated by several examples in the low- and high-temperature regimes. The localization phenomenon for a charged particle is observed. The orbital diamagnetism of quantum system in a dissipative environment is studied. The quantization conditions are found for the angular momentum.

Ionization and electron capture in collisions of bare carbon ions with atomic hydrogen has been studied using the wave-packet continuum discretization approach. The three-body Schrödinger equation governing the collision process is solved using the two-center expansion of the total scattering wave function. Calculations have been performed for the projectile energy range from 1 keV/amu to 10 MeV/amu. While there is excellent agreement with experimental data for the total electron-capture cross section over the entire energy range, the calculated total ionization cross section slightly overestimates the only available measured point. The singly and doubly differential ionization cross sections at 1 and 2.5 MeV/amu are in good agreement with experiment. The differential cross section calculations are extended to lower energies where perturbative methods are expected to fail. At 100 keV/amu impact energy the present singly differential cross section in the ejected angle of the electron shows a pronounced peak in the forward direction. It is concluded that at low incident energies electron capture into the continuum of the projectile strongly enhances electron ejection in the forward direction.

© 2018 IOP Publishing Ltd. Wavepacket continuum-discretisation approach is used to calculate excitation, ionization and electron-capture (ec) cross sections for proton collisions with n = 2 states of atomic hydrogen, where n is the principal quantum number. The approach assumes a classical motion for the projectile and is based on the solution of the three-body Schrödinger equation using the two-center expansion of the total scattering wave function. The scattering wave function is expanded in an orthonormal basis set built from negative-energy eigenstates and wavepacket pseudostates representing the continuum of both the target atom and the atom formed by the projectile after capturing the electron. With a sufficiently large basis, due to the strong coupling between channels, the method produces converged cross sections for direct-scattering, ionization and ec processes simultaneously. For the quasi-elastic transitions, where both orbital and magnetic quantum numbers change, the integrated cross section is infinite. Nevertheless, the corresponding transitions probabilities are finite at any given impact parameter, indicating that the angular differential cross sections can be measured. Calculated cross sections for scattering on the metastable 2s state are compared with other theoretical results obtained using atomic-orbital close-coupling and classical-trajectory Monte Carlo approaches. Considerable disagreement with previous calculations has been found for some transitions at various incident energies.

The classical Hall effect resulting from the impact of external magnetic and electric fields on the non-Markovian dynamics of charge carriers is studied. The dependence of the tangent of the Hall angle on the magnetic field is derived and compared with the experimental data for Zn. The method is proposed to determine experimentally the memory time in a system.

© 2018 Elsevier B.V. The quantum Langevin formalism is used to study the charge carrier transport in a two-dimensional sample. The center of mass of charge carriers is visualized as a quantum particle, while an environment acts as a heat bath coupled to it through the particle–phonon interaction. The dynamics of the charge carriers is limited by the average collision time which takes effectively into account the two-body effects. The functional dependencies of particle–phonon interaction and average collision time on the temperature and magnetic field are phenomenologically treated. The galvano-magnetic and thermo-magnetic effects in the quantum system appear as the results of the transitional processes at low temperatures.

© 2018 American Physical Society. In this work, we develop a wave-packet continuum-discretization approach to ion-atom collisions that includes rearrangement processes. The total scattering wave function is expanded using a two-center basis built from wave-packet pseudostates. The exact three-body Schrödinger equation is converted into coupled-channel differential equations for time-dependent expansion coefficients. In the asymptotic region these time-dependent coefficients represent transition amplitudes for all processes including elastic scattering, excitation, ionization, and electron capture. The wave-packet continuum-discretization approach is ideal for differential ionization studies as it allows one to generate pseudostates with arbitrary energies and distribution. The approach is used to calculate the double differential cross section for ionization in proton collisions with atomic hydrogen. Overall good agreement with experiment is obtained for all considered cases.

© 2017 American Physical Society. The recently developed wave-packet continuum-discretization approach [I. B. Abdurakhmanov, A. S. Kadyrov, and I. Bray, Phys. Rev. A 94, 022703 (2016)2469-992610.1103/PhysRevA.94.022703] is extended to antiproton-helium collisions. The helium target is treated as a three-body Coulomb system using a frozen-core approximation, in which the electron-electron correlation within the target is accounted for through the static interaction. The Schrödinger equation for the helium target is solved numerically to yield bound and continuum states of the active electron. The resulting continuum state is used to construct wave-packet pseudostates with arbitrary energies. The energies of the pseudostates are chosen in a way that is ideal for detailed differential ionization studies. Two-electron target wave functions, formed from the bound and continuum wave-packet states of the active electron and the 1s orbital of He+, are then utilized in the single-center semiclassical impact-parameter close-coupling scheme. A comprehensive set of benchmark results, from angle-integrated to fully differential cross sections for antiproton impact single ionization of helium in the energy range from 1 keV to 1 MeV, is provided. Furthermore, we use our single-center convergent close-coupling approach to study fully differential single ionization of helium by 1-MeV proton impact. The calculated results are in good agreement with recent experimental measurements [H. Gassert, O. Chuluunbaatar, M. Waitz, F. Trinter, H.-K. Kim, T. Bauer, A. Laucke, C. Müller, J. Voigtsberger, M. Weller, Phys. Rev. Lett. 116, 073201 (2016)PRLTAO0031-900710.1103/PhysRevLett.116.073201] for all considered geometries.

© 2017 IOP Publishing Ltd. The atomic hydrogen target has played a pivotal role in the development of quantum collision theory. The key complexities of computationally managing the countably infinite discrete states and the uncountably infinite continuum were solved by using atomic hydrogen as the prototype atomic target. In the case of positron or proton scattering the extra complexity of charge exchange was also solved using the atomic hydrogen target. Most recently, molecular hydrogen has been used successfully as a prototype molecule for developing the corresponding scattering theory. We concentrate on the convergent close-coupling computational approach to light projectiles, such as electrons and positrons, and heavy projectiles, such as protons and antiprotons, scattering on atomic and molecular hydrogen.

Proton stopping power in hydrogen is calculated using a hybrid method. A two-centre convergent close-coupling method is used for calculations involving the proton fraction of the beam, while the Born approximation is used for the hydrogen fraction. For proton-hydrogen collisions rearrangement processes are explicitly included via a two-centre expansion. Hydrogen-hydrogen collisions are calculated including one- and two-electron processes. Despite using the first-order approximation in the hydrogen-hydrogen channel, overall reasonably good agreement with experiment is seen above 100 keV. © Published under licence by IOP Publishing Ltd.

© 2016 American Physical Society. The semiclassical convergent close-coupling approach to ion-atom collisions has been extended to include electron-transfer channels. The approach has been applied to study the excitation and the electron-capture processes in proton-hydrogen collisions. The integral alignment parameter A20 for polarization of Lyman-α emission and the cross sections for excitation and electron-capture into the lowest excited states have been calculated for a wide range of the proton impact energies from 1 keV to 1 MeV. The results are in good agreement with experimental measurements.

Details of the recently developed quantum-mechanical two-center convergent close-coupling approach (Abdurakhmanov et al 2016 J. Phys. B: At. Mol. Phys. 49 03LT01) to proton-hydrogen scattering are presented. The formulation is based on the exact (fully quantum-mechanical) three-body Schrödinger equation. The total scattering wavefunction is expanded using a two-center pseudostate basis. This allows one to include all underlying processes, namely, direct scattering and ionization, electron capture into bound and continuum states of the projectile. The off-shell integration in the coupled-channel Lippmann-Schwinger integral equations emerging from the three-body Schrödinger equation for the scattering wavefunction is taken analytically which greatly reduces computational effort. While the calculated electron capture cross sections are in a good agreement with experiment, some discrepancy exists for the ionization cross sections.

Stopping powers of H, He, H2, and H2O targets for antiprotons have been calculated using a convergent close-coupling method. For He and H2 targets electron-electron correlations are fully accounted for using a multiconfiguration approximation. Two-electron processes are included using an independent-event model. The water molecule is described using a neon-like structure model with a pseudo-spherical potential. Results are tabulated for the purpose of Monte Carlo simulations to model antiproton transport through matter for radiation therapy.

© Published under licence by IOP Publishing Ltd. A fully quantum-mechanical convergent close-coupling approach to proton collisions with atomic hydrogen has been developed. Cross sections for target ionisation and electron capture by the projectile have been calculated in the energy range from 20 keV to 1 MeV. Calculated electron capture cross sections are in good agreement with the experiment, however for ionisation discrepancies between theory and experiment at intermediate energies still remain.

© Published under licence by IOP Publishing Ltd. A time-dependent convergent close-coupling approach to antiproton collisions with noble gas atoms and H2O has been developed using a fully multielectron treatment of the targets. Integrated cross sections for single ionisation have been calculated in a wide range of impact energies from 5 keV up to 2 MeV. Obtained results are in good agreement with experiment.

© Published under licence by IOP Publishing Ltd. The convergent close-coupling method is applied to calculate antiproton and proton stopping cross sections for atomic and molecular targets. Excellent agreement with experimental measurements is obtained for antiprotons in helium while unexpectedly large disagreement is found for the hydrogen molecule, which is inconsistent with very good agreement between our ionisation cross section and the experiment.

We calculate antiproton-impact total single ionization of Ne, Ar, Kr, Xe, and H2O using a time-dependent convergent close-coupling approach. The Ne, Ar, Kr, and Xe atom wave functions are described in a model of six p-shell electrons above a frozen Hartree-Fock core with only one-electron excitations from the outer p shell allowed. For treating the water molecule we use a neonization method recently proposed by Montanari and Miraglia [J. Phys. B: At. Mol. Opt. Phys. 47, 015201 (2014)], which describes the ten-electron water molecule as a dressed Ne-like atom in a pseudospherical potential. In the present work the target states of noble gas atoms and water are obtained using a Laguerre basis expansion. For the noble gas atoms there is reasonably good agreement with the calculated single-ionization cross sections.

© 2015 American Physical Society. ©2015 American Physical Society. Stopping powers of antiprotons in H, He, Ne, Ar, Kr, and Xe targets are calculated using a semiclassical time-dependent convergent close-coupling method. The helium target is treated using both frozen-core and multiconfiguration approximations. The electron-electron correlation of the target is fully accounted for in both cases. Double ionization and ionization with excitation channels are taken into account using an independent-event model. The Ne, Ar, Kr, and Xe atom wave functions are described in a model of six p-shell electrons above a frozen Hartree-Fock core with only one-electron excitations from the outer p shell allowed. Results obtained for helium in the multiconfiguration treatment are in better agreement with experimental measurements than other theories.

Solving the close-coupling equations for electron–atom scattering in momentum space involves the solution of coupled integral equations, which contain principal value singularities. These can be accurately treated numerically using an on-shell subtraction technique. Here we show how the singularities may be taken into account analytically, leading to an alternative approach to the solution of the integral equations. The robustness of the method is demonstrated by considering the S-wave model of e-H scattering across eight orders of magnitude of incident energies.

An ab initio time-dependent convergent close-coupling approach to describing antiproton collisions with molecular hydrogen or the hydrogen molecular ion has been developed. The approach accounts for all possible orientations of the molecular target. Averaging over the molecular orientations is performed fully analytically. For the molecular hydrogen target calculated orientation-averaged total cross sections for single ionization and proton production are compared with several experiments over the energy range of 1-2000 keV. Results for single ionization are in good agreement with experiment, except for the region around the experimental maximum. For proton production reasonable agreement with experiment is observed above 40 keV.

Theoretical confirmation of the experimentally observed phenomenon [Knudsen et al., Phys. Rev. Lett. 105, 213201 (2010)] of target structure-induced suppression of the ionization cross section for low-energy antiproton-molecular hydrogen collisions is given. To this end a novel time-dependent convergent close-coupling approach to the scattering problem that accounts for all possible orientations of the molecular target, has been developed. The approach is applied to study single ionization of molecular hydrogen on the wide energy range from 1 keV to 2 MeV with a particular emphasis on low energies. Results for the orientation-averaged total single ionization cross section are compared with available experimental data and good agreement is found at low (< 20 keV ) and high (> 90 keV ) energies. A minor discrepancy is found within a small energy gap near the maximum of the cross section.

A fully quantal close-coupling integral-equation approach to antiproton-hydrogen collisions has been developed. Integral and fully differential cross sections have been calculated.

The quantum-mechanical convergent close-coupling approach has been used to calculate the fully differential cross section for the single ionization of helium by C6+ ions at 100 MeV/amu. This allows one to test the quality of approximations used in standard approaches to the problem, particularly in geometries that are out of the scattering plane, where there is a strong disagreement between calculations and measurements. The obtained results show that the fully quantum-mechanical treatment of the internuclear motion does not enable one to get any better agreement with experimental data. In addition, we have performed calculations for the precise geometry where experimental data were collected, i.e., in the plane perpendicular to the momentum-transfer direction. We conclude that this rotation also has a minor effect on the shape of the cross section.

This thesis is devoted to extension of the convergent close-coupling (CCC) method to heavy projectiles and its application to the theoretical studies of antiproton scattering on the hydrogen and helium targets.In the Introduction (Chapter 1) the motivation for the study and the current status of antiproton scattering on hydrogen and helium are presented. Other theoretical methods that previously have been applied to these problems are reviewed and their limitations are indicated. The extension of the fully quantummechanical CCC method to ion-atom collisions is presented in Chapter 2. The derivations of the momentum-space coupled-channel Lippmann-Schwinger integral equations from the exact Schr¨odinger equation is given in detail. Transition matrix elements are derived in momentum-space. In Chapter 3 a direct method for solving multi-dimensional Lippmann-Schwinger integral equations without recourse to partial-wave expansion or any other transformation scheme will be described. A direct method has been applied to the antiproton-hydrogen as well as to the proton-hydrogen collisions. In Chapter 4 we solve the full multichannel problem by transforming the coupled-channel integral equations into the impactparameter representation. The scattering amplitude necessary to calculate the differential and total cross sections will be derived from the transition matrix elements. The results of the CCC calculations for antiproton scattering from atomic hydrogen and helium are presented and compared with available experimental data and the results of other calculations in Chapter 5 and Chapter 6, respectively. Finally, in Chapter 7, we draw conclusions arising from this work and indicate future directions for the research.Main results of this work • The convergent close-coupling method has been extended to heavy projectiles and applied to antiproton scattering on atomic hydrogen and helium. • For the first time, the relative motion of the heavy particles in antiproton collisions w

We apply the fully quantum-mechanical convergent close-coupling method to the calculation of antiproton scattering on the ground state of helium. The helium target is treated as a three-body Coulomb system using frozen-core and multiconfiguration approximations. The electron-electron correlation of the target is fully treated in both cases. Though both calculations yield generally good agreement with experiment for the total ionization cross sections, the multiconfiguration results are substantially higher at the lower energies than the frozen-core ones. Calculated longitudinal ejected electron and recoil-ion momentum distributions for the single ionization of helium are in good agreement with the experiment.

A recently developed fully quantal convergent-close-coupling (CCC) approach (Abdurakhmanov et al 2011 J. Phys. B: At. Mol. Opt. Phys. 44 075204) to ion–atom collisions is extended to differential ionization studies. An important feature of the method is that it does not have classical limitations on the relative motion of participating particles. The approach is applied to calculate fully differential, as well as various doubly and singly differential cross sections of ionization in antiproton collisions with atomic hydrogen. The CCC results for various differential cross sections agree reasonably well with the results of the semiclassical CC and the continuum-distorted-wave-eikonal-initial-state approaches,particularly at high energies. However, some discrepancies exist at low energies, where the final state interactions among colliding particles are found to be very important.

A fully quantal integral-equation approach to ion–atom collisions is developed along the lines of the convergent close-coupling approach to electron–atom scattering. The approach starts from the exact three-body Schrödinger equation for the scattering wavefunction and leads to coupled-channel Lippmann–Schwinger equations for the transition amplitudes in the impact-parameter representation, with the relative motion of the heavy particles treated quantum mechanically. The method is applied to calculate antiproton collisions with atomic hydrogen. Integrated total, excitation and ionization cross sections are calculated in the energy range from 1 keV to 1 MeV.