Multiple electron loss by structured heavy ions in fast collisions with complex atoms

A nonperturbative theory of multiple ionization of heavy structured ions in fast collisions with complex neutral atoms is developed. Cross sections are calculated for multiple loss of electrons (up to 15) in collisions of U¹⁰⁺ and U²⁸⁺ with argon atoms and nitrogen molecules. The results are compared with experimental data.     

Continuous electron energy spectra ejected from solid carbon targets bombarded with light and heavy ions

Energy distributions of electrons were measured under an observation angle of 42.3° by bombarding thin carbon foils with protons of 0.5 to 2.5 MeV and with Neon of 10 MeV energies. Comparison of the experimental results with binary-encounter-approximation calculations, taking into account the electron energy loss in the solid, show that the spectra from proton bombardment can be described by this model.     

Multiple scattering of low-energy rare-gas ions at solid surfaces

We have studied the multiple scattering of He⁺, Ne⁺, and Ar⁺ from a TaC(001) surface in the energy region of the order of 1 keV. The experimental data revealed large differences between the energy spectra of these ions. The spectral peak corresponding to quasi-double scattering is clearly observed for Ar⁺ but not observed for Ne⁺. The multiple scattering effect appearing in the energy spectra of rare-gas ions is discussed on the basis of electron exchange between these ions and solid surfaces.     

On the energy loss of fast electrons in thin absorbers

The numerical constants in the Blunck-Leisegang theory for the energy-loss distribution of electrons passing through the matter have been reevaluated accurately. The obtained results give a more precise energy-loss distribution than the usual Blunck-Leisegang theory.     

Multiple scattering of heavy ions,Glauber theory,and optical model

An exact multiple-scattering series for the scattering of two heavy ions is derived and compared to the Glauber approximation. An optical model potential operator is indicated which is an accurate approximation to the multiple-scattering formalism.     

Multiple scattering, parton energy loss, and modified fragmentation functions in deeply inelastic eA scattering

Modified quark fragmentation functions in deeply inelastic eA collisions and their QCD evolution equations are derived for the first time in the framework of multiple parton scattering. Induced radiation gives rise to additional terms in the evolution equations and thus softens the modified quark fragmentation functions. The results in the next-leading-twist depend on both diagonal and off-diagonal twist-four parton distributions and the combination of which clearly manifests the LPM interference pattern. The predicted modification depends quadratically on the nuclear size ( A2/3). Generalization to the case of hot QCD medium is also discussed.     

Impact-parameter dependence of energy loss in light ions scattering by a gold atom

In the measurement of energy loss Q within the collision parameter interval 0.02 Å ? b ? 0.4 Å a plateau of the curve of Q(b) at b ? 0.1 Å has been revealed which may be associated with the polarization of the electronic shell of a gold atom.     

Multiple ionization of atoms and the energy of recoil ions in collisions with fast,multiply charged ions

On the basis of the sudden perturbation approximation and the model of independent electrons, simple analytical expressions are obtained for the cross sections of multiple ionization of atoms and the average energies of recoil ions in collisions between atoms and fast, multiply charged ions in the range of parameters in which the Born approximation is inapplicable. An expression for the energy distribution function of recoil ions is also obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 111–116, April, 1996.     

Inelastic effects in low energy He+ ion scattering from solid and atomic Pb targets

Inelastic energy losses of low energy He ⁺ ions scattered from a solid Pb surface and gas phase Pb are investigated for forward scattering of less than 12°. The gas phase results give rise to loss peaks characteristic of atom-atom collisions, ionization, and/or excitation of the target Pb atom. In comparison, the surface is found to result in a loss peak at an energy which agrees well with the atomic character of the Pb target, although the loss peak is broad. This feature of the surface is explained to be due to excitation of electrons in the 6s or 6p band. Molecular orbital crossing (MO model) is considered to be a reasonable interpretation of the continuous character of the inelastic energy loss.     

Cluster exchange and elastic scattering of heavy ions

The effect of cluster exchange on the nuclear interaction potential is examined. Cluster exchange results in nonlocal interactions that must be added to the direct local potential of the optical model. The dependence of exchange interactions on the parity of relative motion is analyzed. Scattering amplitudes corresponding to nonlocal exchange interactions are calculated in the Born approximation for ¹⁶O + ¹²C scattering.     

Elastic and inelastic scattering of identical heavy ions

The elastic and inelastic scattering of ¹²C, ¹²C, ²⁴Mg, ²⁴Mg, ²⁸Si, ²⁸Si was studied at bombarding energies E_c.m. = 5–18.8, 20–33, 29–36 MeV, respectively. The experimental arrangement includes two position sensitive detectors covering the angular ranges from O₁₂₄ = 20°–70°. The results are compared to calculations within the framework of the diffraction and optical model. A phase shift analysis is performed for the elastic scattering data of the ¹²C+¹²C system. It is shown that a shallow nuclei potential in needed to reproduce the ²⁸Si+²⁸Si results and that the ¹²C, ¹²C scattering shows evidence of resonance formation in the elastic channel.     

Energy loss of heavy ions in carbon foils

The energy loss of Ar, Ti, Kr, Xe, Pb and U ions in the energy range from 0.2 to 1.4 MeV/amu in carbon foils was measured. The results are compared with theoretical and semiempirical estimations.     

Single electron loss by fast ions in helium

The single electron loss cross sections for fast B, N, and Ne ions colliding with He atoms are calculated. In the calculation of the ionization amplitude, the He nucleus screening is taken into account by both the sum rule and the summation over a finite number of excited 1snl (n < 5, l < 2) states and states of the continuous spectrum. The calculated results agree satisfactorily with experimental data.     

Interactions of relativistic heavy ions in thick heavy element targets and some unresolved problems

Interactions of relativistic heavy ions with total energies above 30 GeV in thick Cu and Pb targets (≥ 2 cm) have been studied with various techniques. Radiochemical irradiation experiments using thick Cu targets, both in a compact form or as diluted “2π-Cu targets” have been carried out with several relativistic heavy ions, such as 44 GeV ¹²C (JINR, Dubna, Russia) and 72 GeV ⁴⁰Ar (LBL, Berkeley, USA). Neutron measuring experiments using thick targets irradiated with various relativistic heavy ions up to 44 GeV ¹²C have been performed at the JINR. In addition, the number of “black prongs” in nuclear interactions (due to protons with energies less than 30 MeV and emitted from the target-like interaction partner at rest) produced with 72 GeV ²²Ne ions in nuclear emulsion plates has been measured in the first nuclear interaction of the primary ²²Ne ion and in the following second nuclear interaction of the secondary heavy (Z > 1) ion. Some essential results have been obtained. (1) Spallation products produced by relativistic secondary fragments in interactions ([44 GeV ¹²C or 72 GeV ⁴⁰Ar] + Cu) within thick copper yield fewer products close to the target and many more products far away from the target as compared to primary beam interactions. This applies also to secondary particles emitted into large angles (Θ > 10°). (2) The neutron production of 44 GeV ¹²C within thick Cu and Pb targets is beyond the estimated yield as based on experiments with 12 GeV ¹²C. These rather independent experimental results cannot be understood within well-accepted nuclear reaction models. They appear to present unresolved problems. The text was submitted by the authors in English.