State Selective Scattering Angle Dependent Capture Cross Sections Measured by Cold Target Recoil Ion Momentum Spectroscopy

We have developed a new kind of recoil ion momentum spectroscopy technique, using a precooled supersonic gas jet target, to determine state selective, scattering angle dependent cross sections for swift ion-atom collisions ( 0.25,,1MeVHe²⁺ on He), by measuring the transverse and longitudinal momentum of the recoil ion. A longitudinal momentum resolution of ±0.13a.u. was achieved, about a factor of 30 better than ever obtained before, which enables a clear separation of K and L shell capture. In the transverse direction a resolution corresponding to a projectile scattering angle uncertainty of ΔϑP0ex0ex=0ex0ex±1μrad was obtained.