Multiple scattering of MeV atomic and molecular ions traversing ultrathin films

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Abstract
We have investigated the connection between small-angle multiple scattering and charge-changing processes for fast atomic and molecular ions traversing ultrathin solid targets. Results for the atomic ions show a strong target-thickness dependence of the measured final-charge-state distributions. There is also an accompanying dependence of the multiple-scattering widths upon the final charge state of the ions. These results demonstrate conditions far from equilibrium for these processes. A Monte Carlo simulation of particle motion in the foil is described that successfully accounts for these observations. The same simulation is applied to describe the multiple scattering of diatomic molecular ions and to compute the spread of the internuclear velocity after Coulomb explosion. It is found that the Coulomb repulsion tends to reduce multiple-scattering components along the internuclear axis. Consequences for Coulomb-explosion studies of molecular structures are discussed.