Coupled-channel calculation of stopping powers for intermediate-energy light ions penetrating atomic H and He targets

Abstract

A single-center coupled-channel code based on an expansion in terms of atomic wave functions that includes dynamic curved projectile trajectories is applied to the calculation of stopping powers. Stopping powers and differential ionization cross sections are evaluated for p, H+, He +, and Li'+ projectiles penetrating atomic H and He targets at energies of 10-500 keV/u. The results are compared to experimental data, to predictions of the first-order plane-wave Born approximation, and to results of calculation for excitation of a harmonic oscillator including Barkas corrections. The improvement of the present model to first-order or second-order perturbative treatments as well as the effect of polarization on the projectile trajectories is discussed.

Impact-parameter dependence of the electronic energy loss of fast cluster projectiles

“…3 we see the results of the present model, for two molecule orientations (where φ = 0 • ), for the impact parameter dependence of the mean energy loss of bare (top) and single-zeta screened (bottom) H 2 molecular projectiles, both at 500 keV/amu, colliding with atomic H (full line). We compare our results with full first order molecular SCA (semiclassical approximation, similar to the numerical procedure seen in [21] calculations (squares) and with full first order SCA for two independent protons with the same screen function and impact parameters as used in molecular SCA (dashed line). In our tests, the interatomic distance was set to 2 a. u.…”

Skimming-trajectory effect for energy loss of medium-energy He ions passing along major crystal axes of KI(001) and RbI(001)

“…The energy difference ( E 1−2 ) observed for the [111] incidence and scattered to 65.26 • with respect to surface normal (random) gives the local energy loss of E(K) = 120 eV [see Fig. 1: trajectory (7) We calculated the impact-parameter (b) -dependent energy loss by the coupled-channel method [9]. Shortly, the timedependent Schrödinger equation was solved for one active target electron in the framework of the independent particle model.…”

“…The latter corresponds to the random stopping power. The results obtained experimentally are compared with theoretical predictions based on the coupled-channel method [9,10] that does not rely on a perturbative treatment of the interaction dynamics.…”

Electronic energy loss of channeled ions: The giant Barkas effect

“…Coupled-channel (CC) calculations are the best tool to describe inner-shell ionization and excitation of atoms [26,27] as a function of the impact parameter. These timeconsuming calculations are based on the semiclassical method [34].…”

“…channel method [26,27] to calculate the electronic energy loss for the Si inner-shell electrons. This time-consuming approach takes into account fully the Barkas effect as well as all other higher-order effects for inner-shell electrons.…”