Electron, Positron and Photon Collisions with Atoms and Molecules

Electron scattering from open d-shell atoms/ions, including Fe peak elements

Accurate determination of electron impact excitation rates for low ionization stages of the iron peak elements Fe, Ni and Co are required in the analysis of many astronomical objects, while electron collision data for Sn ions are required in the study of lazer-produced plasmas containing Sn, which are being researched as possible extreme ultraviolet (EUV) sources for the next generation of nanolithography tools. Electron scattering by these open d-shell atoms and ions is complicated by the very large number of target states that arise. This in turn leads to many hundreds, or even thousands, of coupled channels, when relativistic effects are included. In addition, a very fine energy mesh, typically including 15,000 - 20,000 energy points, must be employed to completely delineate the complex resonance structure that occurs in the low energy scattering region.Until recently, such problems would have remained computationally intractable. However, the development of the new parallel R-matrix codes PRMAT and PFARM , coupled with advances in high performance computing, has facilitated the evaluation of accurate collision cross sections and excitation rates for the low-ionised species in the near neutral iron-peak region, which are of significant astrophysical importance. Calculations are currently ongoing for many Fe, Ni and Co ions (open 3-d shells) and ions of Sn (open 4-d shells).