Ilkhom Abdurakhmanov

Coupled-channel integral-equation approach to antiproton–hydrogen collisions

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 Schrodinger 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.

Solving close-coupling equations in momentum space without singularities for charged targets

Abstract The analytical treatment of the Green’s function in the convergent close-coupling method (Bray et al., 2016) has been extended to charged targets. Furthermore, we show that this approach allows for calculation of cross sections at zero channel energy. For neutral targets this means the electron scattering length may be obtained from a single calculation with zero incident energy. For charged targets the non-zero excitation cross sections at thresholds can also be calculated by simply setting the incident energy to the exact threshold value. These features are demonstrated by considering electron scattering on H and He + .

Antiproton stopping power data for radiation therapy simulations.

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.

Accurate solution of the proton-hydrogen three-body scattering problem

An accurate solution to the fundamental three-body problem of proton–hydrogen scattering including direct scattering and ionization, electron capture and electron capture into the continuum (ECC) is presented. The problem has been addressed using a quantum-mechanical two-center convergent close-coupling approach. At each energy the internal consistency of the solution is demonstrated with the help of single-center calculations, with both approaches converging independently to the same electron-loss cross section. This is the sum of the electron capture, ECC and direct ionization cross sections, which are only obtainable separately in the solution of the problem using the two-center expansion. Agreement with experiment for the electron-capture cross section is excellent. However, for the ionization cross sections some discrepancy exists. Given the demonstrated internal consistency we remain confident in the provided theoretical solution.

Hybrid approach to calculating proton stopping power in 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.

Close-coupling approach to antiproton-impact ionisation of H2 with analytical spherical averaging

Integrated cross section for single ionisation of molecular hydrogen by antiproton impact has been calculated in a wide range of impact energies from 1 keV up to 2 MeV using a close-coupling approach. For the first time all possible orientations of the molecular target have been accounted for using an ab initio analytical spherical averaging technique. Obtained results are in good agreement with experiment.

Convergent close-coupling approach to positron and antiproton collisions with atoms

Recent developments in application of the convergent close-coupling approach to antimatter-matter scattering are outlined. These include positron collisions with alkalis and helium, in the ground or metastable states, as well as extension of the method to heavy projectiles, such as antiprotons.

Differential ionization in antiproton–hydrogen collisions within the convergent-close-coupling approach.

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.

Open quantum system in external magnetic field within non-Markovian quantum Langevin approach

Abstract 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.

Galvano- and thermo-magnetic effects at low and high temperatures within non-Markovian quantum Langevin approach

Abstract 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.