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Radiotherapy and dosimetry are techniques used for the treatment of cancer cells and require the proper description of the energy deposition of swift heavy ions when penetrating a biological material. In this work, we report the electronic stopping cross section, by proton radiation, of several complex organic molecules of biological interest that contain, in particular, F and Ar atoms. Our work implements the Harmonic Oscillator approach for the bound electrons through a Floating Spherical Gaussian Orbital description of the molecule in the intermediate to high collision energy within the first Born approximation. In particular, we study the stopping cross section for the following molecules: DNA, guanine, adenine, alanine, glycine, trimethylamine, tissue equivalent gas based on methane and propane, A-150 plastic equivalent material, tissue equivalent liquid, nylon, and air. For complex compounds, where the structure is given in percent by weight (or volume) of molecular fragments, we use a Bragg's-like rule within our model, to determine the electronic stopping cross section. We calculate the orbital and total mean excitation energies for these molecules, finding that it is the orbital mean excitation energy the principal parameter that characterizes the stopping cross section instead of the total molecular mean excitation energy. Our results are in good to excellent agreement to available experimental and theoretical data reported in the literature for these molecules and have an even better agreement than semi-empirical results from approaches like SRIM and PSTAR with the advantage of being analytically simple to implement as well as having a predicting capability for its region of validity. |
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