The Independent Atom Model -- Pixel Counting Method for Ion-Molecule Collisions
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arXiv
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| Hauptverfasser: | , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866911144974745600 |
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| author | Luedde, Hans Juergen Horbatsch, Marko Kirchner, Tom |
| author_facet | Luedde, Hans Juergen Horbatsch, Marko Kirchner, Tom |
| contents | 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_07822 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The Independent Atom Model -- Pixel Counting Method for Ion-Molecule Collisions Luedde, Hans Juergen Horbatsch, Marko Kirchner, Tom Atomic Physics 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. |
| title | The Independent Atom Model -- Pixel Counting Method for Ion-Molecule Collisions |
| topic | Atomic Physics |
| url | https://arxiv.org/abs/2509.07822 |