2025/09/09 by Hans Juergen Luedde, Marko Horbatsch, Luedde, Hans Juergen +3 · 1 citation
Engineering · Physics and Astronomy · #Atomic Physics (physics.atom-ph) #Atomic and Molecular Physics #FOS: Physical sciences #Ion-surface interactions and analysis #X-ray Spectroscopy and Fluorescence Analysis
paper · pdf · doi:10.48550/arxiv.2509.07822
openalex publication_date 2025/09/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The independent atom model - pixel counting method (IAM-PCM) for the description of ion-molecule collisions is reviewed. The method was introduced (in 2016) to improve on the simple additivity rule according to which scattering cross sections for a molecular target can be obtained by summing up the cross sections of the constituent atoms. The key idea of the IAM-PCM is the inclusion of weight factors in the summation, to be determined from a geometrical interpretation of the resultant cross section as a combined area of overlapping atomic contributions, which is calculated via a pixelization technique. We argue here that the IAM-PCM can be conceptualized in a different but equivalent way by associating each pixel in the area decomposition with a scattering event. The calculation of net and charge-state correlated capture and ionization cross sections is explained, and results for 10 keV to 10 MeV proton impact are discussed for a number of targets ranging from compact ten-electron systems to large biomolecules. A previously observed scaling behaviour of the net ionization cross sections is revisited and shown to be captured by a simple parametrization with remarkable accuracy.