CDW-EIS theoretical calculations of projectile deflection for single ionization in highly charged ion–atom collisions (original) (raw)
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Role of elastic projectile-electron scattering in double ionization of helium by fast proton impact
2009
We present a systematic study of atomic four-body fragmentation dynamics. To this end we have measured a variety of multiple differential double ionization cross sections for 6 MeV p + He collisions. The data are compared to a first-order calculation with correlated electrons and to a simulation representing a second-order process, with some experimental results seemingly in favor of the first, others in agreement with the second approach. This apparent conflict can be resolved by accounting for elastic scattering between the projectile and one electron already promoted to the continuum through electron-electron correlation in the first-order process.
Electron correlation in fast ion-impact single ionization of helium atoms
Chinese Physics B, 2015
A four-body distorted-wave approximation is applied for theoretical analysis of the fully differential cross sections (FDCS) for proton-impact single ionization of helium atoms in their ground states. The nine-dimensional integrals for the partial amplitudes are analytically reduced to closed-form expressions or some one-dimensional integrals which can be easily calculated numerically. Calculations are performed in the scattering and perpendicular planes. The influence of the target static electron correlations on the process is investigated using a number of different bound-state wave functions for the ground state of the helium targets. An illustrative computation is performed for 75-keV proton-helium collisions and the obtained results are compared with experimental data and other theoretical predictions. Although for small momentum transfers, the comparison shows a reasonable agreement with experiments in the scattering and perpendicular planes, some significant discrepancies are still present at large momentum transfers in these planes. However, our results are compatible and for some cases, better than those of the other sophisticated calculations.
Fully differential cross sections for the single ionization of helium by ion impact
2003
We present fully differential cross sections for the single ionization of He by C 6+ ions. A time-dependent close-coupling approach is used to describe the two-electron wavefunction in the field of the projectile for a range of impact parameters, and a Fourier transform approach is used to extract fully differential cross sections for a specific momentum transfer. Our calculations are compared to the measurements of Schulz et al (2003 Nature 422 48) and we find very good agreement in the scattering plane and good qualitative agreement in the perpendicular plane. In particular, our calculations in the perpendicular plane find a similar 'double-peak' structure in the angular distributions to those seen experimentally. We also discuss the various checks made on our calculations by comparing to a one-electron time-dependent calculation.
Projectile–Residual-Target-Ion Scattering after Single Ionization of Helium by Slow Proton Impact
Physical Review Letters, 2005
We have measured fully differential single ionization cross sections for 75 keV p He collisions. At this relatively small projectile velocity, signatures of the projectile -residual-target-ion interaction, which are not observable for fast projectiles and for electron impact, are revealed rather sensitively. In fact, this interaction appears to be more important than the postcollision interaction, which so far was assumed to be the most important factor in higher-order effects for slow ion impact. These features are not well reproduced by our three-distorted-wave calculations.
Single and double ionization of helium in heavy-ion impact
Journal of Physics B: Atomic, Molecular and Optical Physics, 2005
We present single-and double-ionization total cross sections for collisions of helium atoms with multiple charged ions. In our study we apply two different approaches, namely the ab initio coupled channel and the classical trajectory Monte Carlo (CTMC) method. We consider bare projectiles with charge states between two and eight with energies between 0.19 and 2.31 MeV/amu. We find that our coupled-channel calculations are very close to the experimental data even for the case when the Coulomb fields are strong. At the same time CTMC models, using different independent-particle approximations, show somewhat larger discrepancies compared to the experimental cross sections. We also present cross sections for 1.44 MeV/amu O q+ (q = 4-7) projectiles.
Physical Review A, 2007
Three-dimensional fully differential cross sections for heavy-particle-impact ionization of helium are examined. Previously, the three-body distorted-wave ͑3DW͒ model has achieved good agreement with experiment in the scattering plane for small momentum transfers, but poor agreement for large momentum transfers. Poor agreement was also observed outside the scattering plane for all momentum transfers. In particular, the 3DW calculations predicted cross sections that were too small both perpendicular to the scattering plane and for large momentum transfers. The important unanswered question concerns the physical effects that cause the significant disagreement between experiment and theory. In previous works, the role of the projectile-ion interaction has been examined. Although the importance of exchange between the ejected electron and the residual bound electrons has been well established, and frequently studied, for electron-impact ionization, the importance of this effect has not been examined for heavy-particle scattering. In this paper we examine the role of this effect for heavy-particle scattering.
2006
In this work we calculate doubly differential cross sections ͑DDCS͒ for single ionization of helium by highly charged ion impact. We study the importance of two-particle interactions in these processes by considering the cross sections as a function of all two-particle subsystems momenta. Experimental DDCSs were obtained recently from kinematically complete experiments on single ionization of He by 100 MeV/ amu C 6+ and 3.6 MeV/ amu Au 24,53+ impact. Furthermore, we evaluated the importance of three-particle interactions by plotting the squared momenta of all three collision fragments simultaneously in a Dalitz plot. Using the first Born and distorted-wave approximations for fully differential cross sections, together with Monte Carlo integration techniques, we were able to reproduce the main features observed in experimental data and to assess the quality of the models implied by the different employed approximations.
CDW and CDW-EIS calculations for FDCSs in highly charged ion impact ionization of helium
2006
In this work we present fully differential cross sections (FDCS) calculations using CDW and CDW-EIS theories for helium single ionization by 100 MeV/amu and 2 MeV/amu C 6+ and 3.6 MeV/amu Au 24+ and Au 53+ ions. We performed our calculations for different momentum transfers and ejected electron energies. We study the influence of the internuclear potential on the ejected electron spectra. We discuss different regimes where the internuclear interaction can or cannot be neglected. We compare our calculations with experimental data available. It is shown that for high impact energy and small momentum transfer, internuclear potential effects can be neglected in FDCSs.
2010
One of the goals in studies of double ionization (DI) of simple atoms by electron or ion impact is to elucidate and assess the different mechanisms that lead to this atomic process. In this work we present an attempt to model the mechanisms beyond the first order in DI of helium by highly charged projectiles. To this end we employ the continuum distorted wave-eikonal initial state (CDW-EIS) formalism joint with a Monte Carlo event generator (MCEG). The MCEG allows us to generate theoretical event files that represent the counterpart of the data obtained from a kinematically complete experiment. Starting from these event files, a new data analysis tool used to contrast theory and experiment in DI, the four-body Dalitz plots, is easily produced. The higher order mechanisms are simulated by considering DI as a sequential process: a single ionization of a helium atom as a first step and another single ionization of a single-charged helium ion as a second step. Some of the features in the experimental data are very well reproduced by these simulations.
2008
We study the effect of final state dynamic correlation in single ionization of atoms by ion impact analyzing fully differential cross sections (FDCS). We use a distorted wave model where the final state is represented by a U 2 type correlated function, solution of a nonseparable three body continuum Hamiltonian. This final state wave function partially includes the correlation of electron-projectile and electron-recoil relative motion as coupling terms of the wave equation. A comparison of fully differential results using this model with other theories and experimental data reveals that inclusion of dynamic correlation effects have little influence on FDCS, and do not contribute to a better description of available data in the case of electronic emission out-of scattering plane.