Charge-changing cross sections for Pb and Xe ions at velocities up to 4 ×109cm/sec

Abstract

We have made a comprehensive study of charge-changing cross sections in N2 of Pb and Xe ions at velocities near 4 X 10 cm/sec. We determine the velocity, ionization state, and Z dependence of the capture and ionization cross sections and make an extensive comparison with theory.Capture or loss of an electron by a fast very heavy complex ion colliding with an atom is one of the more refractory problems in atomic collisions. " For very heavy ions at velocities «10 cm/sec only a small amount of experimental information is available, Also, there is a general perception that theoretical models used for lighter and simpler ions may be inadequate. 2 In this Communication we present the first comprehensive study of charge-changing collisions of very heavy ions at velocities above 10 cm/sec.From experimental measurements of Pb (Z =82) and Xe (Z =54) ions in N~at velocities (relative to the speed of light) of p=v/c =0.134 and p=0.099, and Xe at p =0.072 we extract a total of 178 cross sections. We determine the velocity, ion charge, and nuclear charge dependence of these cross sections.

Scaling laws for single and multiple electron loss from projectiles in collisions with a many-electron target

“…For the projectile charge, vastly different dependences were found. The cross sections for highly charged ions are found to decrease extremely fast with increasing projectile charge, e.g., q −8-10 in some cases [16][17][18] but slower q −3-4.4 in other cases [19]. In contrast, recent CTMC calculations [3,4] and experiments [4] imply that low-charge heavy ions have a much slower dependence of approximately q −1 .…”

“…This is consistent with what Bohr predicted for medium weight targets, but Bohr obtained his formula using assumptions that are not applicable at high velocities. Experimentally, except for light, few-electron projectiles, the only studies of the velocity dependence for electron loss from fast, heavy ions are by Olson et al [3] for loss from 2 to 9 MeV/ u Xe 18+ ions and by Alonso and Gould [19] for Pb q+ ions ͑q =36-51͒ and Xe q+ ions ͑q =27-42͒ for velocities v / c between 0.099 and 0.134. In both cases, collisions were with N 2 .…”

Relativistic Uranium Beams--the Bevalac Experience

“…Therefore, one must ascertain what vacuum is necessary for survival of partially stripped ions. An extensive set of cross section measurements 11 at the SuperHlLAC has generated the data shown in eliminate atmospheric structural stresses on the fiberglass assemblies. The nested-box assemblies were installed throughout the Bevatron, except for the straight sections where the RF system, inflection system and plunging extraction magnets were located.…”

Electron capture in intermediate-to-fast heavy ion collisions with neutral atoms

“…For very heavy ions, experimental data on EC cross sections are very scarce and were mainly obtained at the GSI accelerator facility [10][11][12][13], the Super-HILAC machine at Lawrence Livermore National Laboratory in Berkeley [14] and the Texas A&M Cyclotron [15][16][17]. We note that in the case of highly charged, heavy ions, the contribution of multiple-electron capture, reaction 1, can be significant and increases with the ion charge.…”

“…Experiment: s single-electron and d total capture cross sections[10]; j total cross section[14]. Dashed curves: Schlachter formula (6) for a single-electron capture.…”