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

Abstract

Using measured cross sections, empirical scaling laws are extracted for projectile stripping induced by collisions with a many-electron target. By scaling both the cross sections and the impact velocities, it is shown that a single universal curve can be used to fit data for single and multiple electron loss from negative ions, neutral particles, and singly or multiply charged positive ions. The scaling applies to projectiles ranging from hydrogen to uranium and collision energies ranging from below keV/ u to hundreds of MeV/ u. At high energies, existing data are consistent with a v −1 impact velocity dependence for scaled velocities less than 10. Limited data imply that above 10 the velocity dependence becomes v −2 . Using our universal curve, cross sections are predicted for electron loss from low-charge-state heavy ions at 20 and 100 MeV/ u.

Electron loss and capture from low-charge-state oxygen projectiles in methane

“…The data for H 0 are slightly smaller than the present data for O 0 , as expected from the scaling law of Santos and DuBois [12] which predicts that the electron loss cross scale as σ ∼N eff 0.4 /I p , where N eff is the effective number of the outermost electrons in the projectile and I p is the projectile ionization potential. Again, the results obtained in the freecollision model are in close agreement with the experimental data for single-, double-and total-electron-loss cross sections.…”

“…On the other hand, theoretical studies which try to take into account the several processes involved in the dynamics of collisions of multi-electronic projectiles and atoms and molecules in the low-to intermediate-velocity regime are even scarcer. For these reasons, several efforts concerning scaling laws for single-and multiple-electron loss have been reported [12][13][14][15][16]. The formulas are considered to have predictive capabilities with accuracy within a factor of 2.…”

Multiple ionization of fast heavy ions by neutral atoms in the energy deposition model

“…Intensive experimental studies of multiple ionization of fast heavy ions by neutral atoms have been carried out mainly at the GSI accelerator facility and the Texas A&M cyclotron (see e.g., [6][7][8][9][10][11][12][13]14] and references therein). These studies were theoretically supported by nCTMC (n-body classicaltrajectory Monte Carlo) calculations (see, [10-13, 15, 16]).…”

Ionization cross-sections for ion–atom collisions in high-energy ion beams

“…While specific values of the cross-sections for various pairs of projectile ions and target atoms have been measured at several energies [2,3,6,7], the study of the scaling of cross-sections with energy and target or projectile nucleus is only now underway [8,9]. When experimental data and theoretical calculations are not available, approximate formulas are frequently used.…”