2020/07/27 by H. J. Lüdde, Lüdde, Hans Jürgen, Alba Jorge +5 · 1 citation
Chemistry · Engineering · Physics and Astronomy · #Atomic Physics (physics.atom-ph) #Atomic and Molecular Physics #Biological Physics (physics.bio-ph) #FOS: Physical sciences #Ion-surface interactions and analysis #Mass Spectrometry Techniques and Applications
paper · pdf · doi:10.48550/arxiv.2007.13497
openalex publication_date 2020/07/27 · openalex created_date 2022/07/24 · openalex updated_date 2026/07/28
A model for the description of proton collisions from molecules composed of\natoms such as hydrogen, carbon, nitrogen, oxygen and phosphorus (H, C, N, O, P)\nwas recently extended to treat collisions with multiply charged ions with a\nfocus on net ionization. Here we complement the work by focusing on net\ncapture. The ion-atom collisions are computed using the two-center basis\ngenerator method. The atomic net capture cross sections are then used to\nassemble two models for ion-molecule collisions: an independent atom model\n(IAM) based on the Bragg additivity rule (labeled IAM-AR), and also the\nso-called pixel-counting method (IAM-PCM) which introduces dependence on the\norientation of the molecule during impact. The IAM-PCM leads to significantly\nreduced capture cross sections relative to IAM-AR at low energies, since it\ntakes into account the overlap of effective atomic cross sectional areas. We\ncompare our results with available experimental and other theoretical data\nfocusing on water vapor (H2O), methane (CH4) and uracil (C4H4N2O2). For the\nwater molecule target we also provide results from a classical-trajectory Monte\nCarlo approach that includes dynamical screening effects on projectile and\ntarget. For small molecules dominated by a many-electron atom, such as carbon\nin methane, or oxygen in water we find a saturation phenomenon for higher\nprojectile charges (Q = 3) and low energies, where the net capture cross\nsection for the molecule is dominated by the net cross section for the\nmany-electron atom, and the net capture cross section is not proportional to\nthe total number of valence electrons.\n