Elastic angular differential cross sections for quasi-oneelectron collision systems at intermediate energies: (Na\u3csup\u3e+\u3c/sup\u3e, Li\u3csup\u3e+\u3c/sup\u3e)+H and (Mg\u3csup\u3e+\u3c/sup\u3e, Be\u3csup\u3e+\u3c/sup\u3e)+He

Measurements of elastic angular differential cross sections have been carried out for four quasi-one-electron collision systems at intermediate energies. Data are presented for Na++H collisions at laboratory energies of 35.94, 51.75, 63.89, and 143.75 keV, for Li++H collisions at energies of 19.44 and 43.75 keV, for Mg++He collisions at energies of 30, 66.7, and 150 keV, and for Be++He collisions at an energy of 56.25 keV. The highest energy in each case corresponds to a projectile velocity of (1/2 a.u. Born and Eikonal calculations, in which we model the projectile ion as a heavy structureless ion of charge +1e, are also presented. Our model calculations are in fair agreement with the experimental data over the range of measured scattering angles

Angular-differential studies of excitation in quasi-oneelectron collisions at high energy

Qualitative differences have been observed between two types of quasi-one-electron collision systems. We have studied valence-electron excitation at high energy (relative collision velocities up to 0.5 a.u.) in the Mg++He and Na++H collision systems, and find that while Mg++He collisions are dominated by direct excitation, the Na++H collisions exhibit significant molecular excitation, even at the highest velocities. This behavior can be understood in terms of the molecular structure of the respective collision complexes, and the energy separation between the ground and first excited states of the valence electron

State-selective capture in collisions of protons with noble gases

We have measured coincidences between neutral H atoms and Lyman-α photons for collisions between 50-keV protons and noble gases as a function of the projectile scattering angle. The coincidences are dominated by capture to the 2p state of the projectile. While the total cross sections depend strongly on the target, the shape of the angular distribution of the differential cross sections was found to depend only weakly on that parameter. The data indicate that electrons are captured predominantly from the outermost shell of the target atom for the collision systems studied here

Angular-differential cross sections for H(2\u3ci\u3ep\u3c/i\u3e) formation in intermediate-energy proton-helium collisions

Angular-differential cross sections for charge transfer with simultaneous emission of a photon in collisions of protons with helium atoms have been measured. The incident proton energies were 25, 50, and 100 keV and the center-of-mass scattering angles were between 0 and 2.0 mrad. In the experiment, hydrogen atoms that scattered through an angle θ were detected in coincidence with photons emitted perpendicular to the scattering plane with a wavelength between 1140 and 1400 Å. Differential cross sections for capture into the 2p state of the hydrogen atom were determined from the variation in the coincidence signal with θ. The experimental results are compared with the results of a classical trajectory Monte Carlo (CTMC) simulation and with the results of a calculation for H(2p) capture using the Coulomb-Brinkman-Kramers (CBK) approximation. The agreement between the experimental results and the CTMC calculation is good at all three energies while the agreement between the shape of the data and the CBK calculation is good at 50 and 100 keV

Angular differential cross sections for the excitation of 1\u3csup\u3e1\u3c/sup\u3eS helium to the 2\u3csup\u3e1\u3c/sup\u3eS and 2\u3csup\u3e1\u3c/sup\u3eP states by 25- to 100-keV-proton impact

Angular differential cross sections for the proton-impact excitation of ground-state helium (11S) to the 21S and 21P states have been measured for the first time in the energy range 25 to 100 keV with use of the energy-loss technique. The data indicate that, for very small scattering angles, at 25 keV the 21S differential cross section is greater than the 21P differential cross section. For impact energies greater than 50 keV, the 21P differential cross section clearly dominates over the 21S cross section in the very small scattering angle region. The present data have been numerically summed and integrated to compare with previous absolute experimental measurements on related processes. These are in very good agreement with the present results. An eight-state impact parameter calculation incorporating the electron-capture channel was performed and resulted in the best agreement with the experimentally determined differential cross sections

Experimental and theoretical (e,2e) ionization cross sections for a hydrogen target at 75.3 eV incident energy in a coplanar asymmetric geometry

Very recently it was shown that the molecular three-body distorted wave (M3DW) approach gives good agreement with the shape of the experimental data for electron-impact ionization of H2 in a coplanar symmetric geometry, providing the incident electrons have an energy of 35 eV or greater. One of the weaknesses of these studies was that only the shape of the cross section could be compared to experiment, since there was no absolute or relative normalization of the data. Here we report a joint experimental/theoretical study of electron-impact ionization of H2 in a coplanar asymmetric geometry where the energy of the incident electron was fixed, and different pairs of final state electron energies were used. In this case, the experimental data can be normalized such that only one renormalization factor is required. It is shown that the M3DW is pretty good in agreement with experiment. However, a better treatment of polarization and exchange between the continuum and bound state electrons is required before quantitative agreement between experiment and theory is achieved

Effects of the final-state electron-ion interactions on the fully differential cross sections for heavy-particle-impact ionization of helium

Three-dimensional fully differential cross sections for heavy-particle-impact ionization of helium are examined. Previously, the three-body distorted-wave (3DW) 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