Multiple scattering and wake effects in interactions of fast diatomic molecules with thin foils

At small angles between the diatomic-cluster axis and the direction of motion the multiple scattering on medium atoms is shown to be of a coherent character and intensifies considerably the wake effects. As a consequence, even at small dwell times on the energy-angle plane singular curves arise, on which the break-up particle distribution function has integrable singularities. At confluence points of the symmetric branches of the curves the singularities strengthen ("wake focalizing"). The theory of the phenomenon is based on the use of an effective Hamiltonian including the coherent multiple scattering and the wake-potential interactions. The motion of the centre-of-mass (CM) is described by a Fokker-Planck-type equation. Our analysis allowed us to find the positions and the structure of the distribution function singularities depending on the experimental conditions. The explicit dependence of the number of fast ions of the H ₂⁺ or ⁴HeH ⁺ type, transmitted through a foil in the R regime, upon parameters of the incident ions and the foil is established theoretically.