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Nicolanti F, Caccia B, Cartoni A, Emfietzoglou D, Faccini R, Incerti S, Kyriakou I, Satta M, Tran HN, Mancini-Terracciano C. Calculation of electron interaction models in N 2 and O 2. Phys Med 2023; 114:102661. [PMID: 37703804 DOI: 10.1016/j.ejmp.2023.102661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 06/19/2023] [Accepted: 08/05/2023] [Indexed: 09/15/2023] Open
Abstract
Cosmic rays have the potential to significantly affect the atmospheric composition by increasing the rate and changing the types of chemical reactions through ion production. The amount and states of ionization, and the spatial distribution of ions produced are still open questions for atmospheric models. To precisely estimate these quantities, it is necessary to simulate particle-molecule interactions, down to very low energies. Models enabling such simulations require interaction probabilities over a broad energy range and for all energetically allowed scattering processes. In this paper, we focus on electron interaction with the two most abundant molecules in the atmosphere, i.e., N2 and O2, as an initial step. A set of elastic and inelastic cross section models for electron transportation in oxygen and nitrogen molecules valid in the energy range 10 eV - 1 MeV, is presented. Comparison is made with available theoretical and experimental data and a reasonable good agreement is observed. Stopping power is calculated and compared with published data to assess the general consistency and reliability of our results. Good overall agreement is observed, with relative differences lower than 6% with the ESTAR database.
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Affiliation(s)
- F Nicolanti
- Physics Dep., Sapienza U. of Rome, p.le Aldo Moro, 5, 00185, Rome, Italy; INFN, Sec. of Rome, p.le Aldo Moro, 2, 00185, Rome, Italy.
| | - B Caccia
- ISS(Italian National Institute of Health), V. Regina Elena, 299, 00161, Rome, Italy
| | - A Cartoni
- Chemistry Dep., Sapienza U. of Rome, p.le Aldo Moro, 5, 00185, Rome, Italy
| | - D Emfietzoglou
- Med. Phys. Lab., Dept of Medicine, University of Ioannina, 45110, Ioannina, Greece
| | - R Faccini
- Physics Dep., Sapienza U. of Rome, p.le Aldo Moro, 5, 00185, Rome, Italy; INFN, Sec. of Rome, p.le Aldo Moro, 2, 00185, Rome, Italy
| | - S Incerti
- Université de Bordeaux, CNRS, LP2I Bordeaux, UMR 5797, Chemin du Solarium, 19, 33170, Gradignan, France
| | - I Kyriakou
- Med. Phys. Lab., Dept of Medicine, University of Ioannina, 45110, Ioannina, Greece
| | - M Satta
- Chemistry Dep., Sapienza U. of Rome, p.le Aldo Moro, 5, 00185, Rome, Italy; ISMN-CNR, p. Aldo Moro, 7, 00185, Rome, Italy
| | - H N Tran
- Université de Bordeaux, CNRS, LP2I Bordeaux, UMR 5797, Chemin du Solarium, 19, 33170, Gradignan, France
| | - C Mancini-Terracciano
- Physics Dep., Sapienza U. of Rome, p.le Aldo Moro, 5, 00185, Rome, Italy; INFN, Sec. of Rome, p.le Aldo Moro, 2, 00185, Rome, Italy
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Bui A, Bekerat H, Childress L, Sankey J, Seuntjens J, Enger SA. Effects of incoming particle energy and cluster size on the G-value of hydrated electrons. Phys Med 2023; 107:102540. [PMID: 36804695 DOI: 10.1016/j.ejmp.2023.102540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 01/29/2023] [Accepted: 02/01/2023] [Indexed: 02/18/2023] Open
Abstract
In hydrated electron (e-aq) dosimetry, absorbed radiation dose to water is measured by monitoring the concentration of radiation-induced e-aq. However, to obtain accurate dose, the radiation chemical yield of e-aq, G(e-aq), is needed for the radiation quality/setup under investigation. The aim of this study was to investigate the time-evolution of the G-values for the main generated reactive species during water radiolysis using GEANT4-DNA. The effects of cluster size and linear energy transfer (LET) on G(e-aq) were examined. Validity of GEANT4-DNA for calculation of G(e-aq) for clinically relevant energies was studied. Three scenarios were investigated with different phantom sizes and incoming electron energies (1 keV to 1 MeV). The time evolution of G(e-aq) was in good agreement with published data and did not change with decreasing phantom size. The time-evolution of the G-values increases with increasing LET for all radiolytic species. The particle tracks formed with high-energy electrons are separated and the resulting reactive species develop independently in time. With decreasing energy, the mean separation distance between reactive species decreases. The particle tracks might not initially overlap but will overlap shortly thereafter due to diffusion of reactive species, increasing the probability of e-aq recombination with other species. This also explains the decrease of G(e-aq) with cluster size and LET. Finally, if all factors are kept constant, as the incoming electron energy increases to clinically relevant energies, G(e-aq) remains similar to its value at 1 MeV, hence GEANT4-DNA can be used for clinically relevant energies.
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Affiliation(s)
- Alaina Bui
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montréal, Quebec, Canada.
| | - Hamed Bekerat
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montréal, Quebec, Canada; Radiation Oncology Department, Jewish General Hospital, Montréal, Quebec, Canada
| | - Lilian Childress
- Department of Physics, McGill University, Montréal, Quebec, Canada
| | - Jack Sankey
- Department of Physics, McGill University, Montréal, Quebec, Canada
| | - Jan Seuntjens
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montréal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montréal, Quebec, Canada
| | - Shirin A Enger
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montréal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montréal, Quebec, Canada; Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Quebec, Canada
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