# Proton-impact-induced electron emission from biologically relevant molecules studied with a screened independent atom model

## TL;DR

This study calculates proton-impact ionization cross sections for biologically relevant molecules using a new independent-atom-model method, achieving good agreement with experiments and providing simple analytical formulas for practical use.

## Contribution

It introduces a novel pixel counting method within the independent-atom model to accurately predict ionization cross sections for complex biological molecules.

## Key findings

- Good agreement with experimental data for various molecules.
- A new scaling method improves cross section predictions.
- Simple analytical formulas can represent results within 3% accuracy.

## Abstract

We use the recently introduced independent-atom-model pixel counting method to calculate proton-impact net ionization cross sections for a large class of biologically relevant systems including pyrimidines, purines, amino acids, and nucleotides from 10 keV to 10 MeV impact energy. Overall good agreement with experimental data, where available, is found. A scaling prescription that involves coefficients derived from the independent atom model is shown to represent the cross section results better than scalings based on the number of (bonding) valence electrons of the target molecules. It is shown that the scaled net ionization cross sections of the proton-nucleotide collision systems can be represented in terms of a simple analytical formula with four parameters to within 3% accuracy.