Target Dependence of Binary Encounter Electron Peak Anomalies in Collisions of Partially Stripped Heavy Ions with Molecular Hydrogen and Noble Gases

A systematic search was performed for the manifestation of quantum interference effects in the shape and angular distribution of the binary-encounter electron peak in collisions of partially stripped, or structured, heavy ions with noble gases and molecular hydrogen. The ionic species investigated were Cu5+,19+, I7+,23+, Au11+,29+ and U13+, all at the same nominal velocity equivalent to 0.6 MeV amu-1. Experimental double-differential cross sections for secondary electron emission in the binary encounter energy region are compared with a simple model based on the elastic scattering of quasi-free target electrons in the projectile field as well as with results of impulse approximation (IA) calculations. While these calculations provide a good qualitative overall description of the observed quantum effects for noble gas targets, this is not the case for H2 targets. An attempt was made to incorporate target molecular structure into the impulse approximation code by allowing the binary electron amplitudes from each of the hydrogen atoms, assumed to constitute the H2 molecule, to interfere. This approach, while demonstrating the strong influence of molecular orientation upon the intermediate energy region of the cross sections, did not meet with success, thereby indicating the necessity to consider the final-state interaction of the binary electron with the two protons of the residual H2+ or H22+ target. © 1995 IOP Publishing Ltd

Differential Cross Sections for the Production of Highly Charged Recoil Ions in 10 Mev F⁸⁺ → Ne Collisions

Using recoil-ion momentum spectroscopy (rims), we have measured differential cross sections for the production of highly charged Ne ions in collisions with 10 MeV Fs+ as a function of the recoil-ion transverse momentum and charge state. In addition, the outgoing projectiles were charge-state analyzed and detected in coincidence with the Ne recoil-ions. Thus, different reaction channels like direct ionization, single- and double-electron capture by the projectile could be separated. The recoil-ion transverse momentum p£ was determined with an accuracy comparable to a projectile scattering angle resolution of 2.5 x 10 5 rad. The experimental data are compared to results of classical many-particle (mctmc) and semiclassical quantum-statistical calculations. © 1994 IOP Publication Ltd

Single photon induced symmetry breaking of H2 dissociation

H{sub 2}, the smallest and most abundant molecule in the universe, has a perfectly symmetric ground state. What does it take to break this symmetry? Here we show that the inversion symmetry can be broken by absorption of a linearly polarized photon, which itself has inversion symmetry. In particular, the emission of a photoelectron with subsequent dissociation of the remaining H{sub 2}{sup +} fragment shows no symmetry with respect to the ionic H+ and neutral H atomic fragments. This result is the consequence of the entanglement between symmetric and antisymmetric H{sub 2}{sup +} states resulting from autoionization. The mechanisms behind this symmetry breaking are general for all molecules

Dynamics Of Multiply Charged Ion-atom Collisions: U³²⁺+Ne

Measurements and calculations are presented for the mean recoil-ion energies of Nei+ produced in 1.4 MeV u-1 (0.33 GeV) collisions of U32+ with Ne. Recoil-ion charge states i=1-8 have been observed; the mean recoil energies are low and do not exceed 1 eV until i\u3e6. Calculations employing a newly developed n-body classical trajectory Monte Carlo method are found to yield results in qualitative agreement with the recoil-ion experiment. Calculations also are presented for the ionisation and charge exchange cross sections, the projectile energy loss and the ejected-electron energy and angular spectra. The importance of fast ejected electrons in the dynamics of energetic multiply charged ion-atom collisions is noted