Positron scattering from O₂

Abstract

We report on recent cross section results for positron scattering from molecular oxygen (O2). Total cross sections (TCSs) were measured with a positron spectrometer in the energy range from 0.1 to 50 eV and with an energy resolution of the positron beam of ∼0.25 eV. In addition, TCSs as well as elastic and inelastic integral cross sections were computed within the independent atom model and screening corrected additivity rule approach, with both dipole and dipole plus quadrupole polarization potentials, between 1 and 1000 eV impact energy. An overall fair level of accord is found between the experimental TCS and that calculated with the model that includes the quadrupole term. Comparison to earlier measurements shows very good agreement with the present measured TCS and fair agreement with the TCS computed with our most physical model above ∼8 eV. Conversely, we find only a marginal level of accord when comparing our experimental TCS with previous computations, while the present TCS calculated with the dipole plus quadrupole potentials appears to agree reasonably well with most of the existing theoretical results above ∼100 eV.

Total, elastic, and inelastic cross sections for positron and electron collisions with tetrahydrofuran

“…57 In those studies, reasonable agreement was found with the reported experimental results. In addition, we have also investigated the molecular systems NO 2 , N 2 O, 3-hydroxy-tetrahydrofuran, 58 and pyrimidine with our IAM-SCAR approach, and while the results from those studies are waiting to be written up for publication they are generally found to be in quite reasonable agreement with the available TCS data.…”

Experimental and theoretical cross sections for positron collisions with 3-hydroxy-tetrahydrofuran

“…More recently, the IAM-SCAR method has also been successfully applied to positron scattering studies from argon, 35 diatomics such as molecular oxygen, 36 and to macro-molecules, such as THF, 9 where fair agreement was typically found with the reported measurements. As the details of our theory have already been presented in those papers, here we only briefly summarize the method behind our calculations.…”

“…(1) represents the elastic scattering process and consists of the electrostatic interaction term, V s (r), and the polarization term, V p (r), whereas the imaginary part accounts for inelastic processes which are considered as absorptions, V a (r), from the incident positron beam. The details of our static, polarization and absorption potentials have recently been described by Chiari et al 36 and therefore are not revisited here. Nevertheless, it is worthwhile to stress that, unlike with electrons, for positron collisions the definition of the energy for the absorption threshold ( ) is somewhat controversial.…”

Cross-section calculations for positron scattering from pyrimidine over an energy range from 0.1 to 10000 eV

“…However studies regarding positron scattering are scarcer and the majority of them have been restricted to a limited energy domain, either at low [6] or high energies [7]. Moreover, the computational analysis of positron scattering with polyatomic molecules is still fairly limited to relatively simple molecular structures [7][8][9]. In order to extend our knowledge of radiationinduced damage in biomolecular systems and provide relevant parameters for radiation-based biomedical applications, it is necessary to apply these models to increasingly more complicated biomolecules.…”