Electron impact excitation of the a 3B1u electronic state in C2H4: an experimentally benchmarked system?

We report on differential and integral cross section measurements for the electron impact excitation of the lowest-lying triplet electronic state (ã 3B1u) in ethylene (C2H4). The energy range of the present experiments was 9 eV–50 eV, with the angular range of the differential cross section measurements being 15°–90°. As the ground electronic state of C2H4 is a 1Ag state, this singlet → triplet excitation process is expected to be dominated by exchange scattering. The present angular distributions are found to support that assertion. Comparison, where possible, with previous experimental results from the University of Fribourg group shows very good agreement, to within the uncertainties on the measured cross sections. Agreement with the available theories, however, is generally marginal with the theories typically overestimating the magnitude of the differential cross sections. Notwithstanding that, the shapes of the theoretical angular distributions were in fact found to be in good accord with the corresponding experimental results

The role of pyrimidine and water as underlying molecular constituents for describing radiation damage in living tissue: A comparative study

8 págs.; 7 figs.; 2 tabs.© 2015 AIP Publishing LLC. Water is often used as the medium for characterizing the effects of radiation on living tissue. However, in this study, charged-particle track simulations are employed to quantify the induced physicochemical and potential biological implications when a primary ionising particle with energy 10 keV strikes a medium made up entirely of water or pyrimidine. Note that pyrimidine was chosen as the DNA/RNA bases cytosine, thymine, and uracil can be considered pyrimidine derivatives. This study aims to assess the influence of the choice of medium on the charged-particle transport, and identify how appropriate it is to use water as the default medium to describe the effects of ionising radiation on living tissue. Based on the respective electron interaction cross sections, we provide a model, which allows the study of radiation effects not only in terms of energy deposition (absorbed dose and stopping power) but also in terms of the number of induced molecular processes. Results of these parameters for water and pyrimidine are presented and compared.This research was supported by the Australian Research Council (ARC) through its Centres of Excellence Program. D.B.J. thanks the ARC for provision of a Discovery Early Career Researcher Award. We also acknowledge the support of the Spanish Ministerio de Economia y Competitivad under Project No. FIS 2012-31230 and the European Union COST Actions (MP1002 and CM1301). P.L.V. acknowledges the Portuguese Foundation for Science and Technology (FCTMEC) through research grants PTDC/FIS-ATO/1832/2012, UID/FIS/00068/2013, and SFRH/BSAB/105792/2014. P.L.V. also acknowledges his Visiting Professor position at Flinders University, Adelaide, South Australia.Peer Reviewe

Excitation of electronic states in tetrahydrofuran by electron impact

We report on differential and integral cross section measurements for the electron impact excitation of the three lowest lying Rydberg bands of electronic states in tetrahydrofuran. The energy range of the present experiments was 15–50 eV with the angular range of the differential cross section measurements being 15°–90°. The important effects of the long-range target dipole moment and the target dipole polarizability, on the scattering dynamics of this system, are evident from the present results. To the best of our knowledge, there are no other theoretical or experimental data against which we can compare the cross section results from this study

Differential cross sections for the electron impact excitation of pyrimidine

We report on differential cross section (DCS) measurements for the electron-impact excitation of the electronic states of pyrimidine. The energy range of the present measurements was 15–50 eV with the angular range of the measurements being 10°–90°. All measured DCSs displayed forward-peaked angular distributions, consistent with the relatively large magnitudes for the dipole moment and dipole polarizability of pyrimidine. Excitations to triplet states were found to be particularly important in some energy loss features at the lower incident electron energies. To the best of our knowledge there are no other experimental data or theoretical computations against which we can compare the present results

Electron-scattering cross sections for collisions with tetrahydrofuran from 50 to 5000 eV

In this paper, we report on total electron tetrahydrofuran (C4 H8 O) scattering cross-section measurements for energies in the range from 50 to 5000 eV with experimental errors of about 5%. In addition, integral elastic and inelastic cross sections have been calculated over a broad energy range (1-10000 eV), with an optical potential method assuming a screening-corrected independent atom representation. Partial and total ionization cross sections have been also obtained by combining simultaneous electron and ion measurements with a time-of-flight analysis of the ionic induced fragmentation. Finally, an average energy distribution of secondary electrons has been derived from these measurements in order to provide data for modeling electron-induced damage in biomolecular systems. © 2009 The American Physical Society.de Educación y Ciencia Plan Nacional de Física, This study has been partially supported by the following research projects and institutions: Ministerio Project No. FIS2006-00702, Consejo de Seguridad Nuclear CSN, European Science Foundation COST Action CM0601 and EIPAM Project, Acciones Integradas Hispano-Portuguesas Project No. HP2006-0042Peer Reviewe

Electron-scattering cross sections for collisions with tetrahydrofuran from 50 to 5000 eV

In this paper, we report on total electron tetrahydrofuran (C4H8O) scattering cross-section measurements for energies in the range from 50 to 5000 eV with experimental errors of about 5%. In addition, integral elastic and inelastic cross sections have been calculated over a broad energy range (1–10 000 eV), with an optical potential method assuming a screening-corrected independent atom representation. Partial and total ionization cross sections have been also obtained by combining simultaneous electron and ion measurements with a time-of-flight analysis of the ionic induced fragmentation. Finally, an average energy distribution of secondary electrons has been derived from these measurements in order to provide data for modeling electron-induced damage in biomolecular systems

TRAX-CHEMxt: Towards the Homogeneous Chemical Stage of Radiation Damage

The indirect effect of radiation plays an important role in radio-induced biological damages. Monte Carlo codes have been widely used in recent years to study the chemical evolution of particle tracks. However, due to the large computational efforts required, their applicability is typically limited to simulations in pure water targets and to temporal scales up to the µs. In this work, a new extension of TRAX-CHEM is presented, namely TRAX-CHEMxt, able to predict the chemical yields at longer times, with the capability of exploring the homogeneous biochemical stage. Based on the species coordinates produced around one track, the set of reaction–diffusion equations is solved numerically with a computationally light approach based on concentration distributions. In the overlapping time scale (500 ns–1 µs), a very good agreement to standard TRAX-CHEM is found, with deviations below 6% for different beam qualities and oxygenations. Moreover, an improvement in the computational speed by more than three orders of magnitude is achieved. The results of this work are also compared with those from another Monte Carlo-based algorithm and a fully homogeneous code (Kinetiscope). TRAX-CHEMxt will allow for studying the variation in chemical endpoints at longer timescales with the introduction, as the next step, of biomolecules, for more realistic assessments of biological response under different radiation and environmental conditions

Electron interactions with tetrahydrofuran

In this paper, we summarize our recent experimental and theoretical results on electron scattering from gaseous tetrahydrofuran (THF). Electron-impact ionization and total scattering cross sections were determined experimentally for energies between 50-5000 eV. Electron energy loss spectra were measured in the keV range using a transmission beam technique and for smaller energies (15-50 eV) with a crossed-beam apparatus. Using an optical potential method assuming the screening-corrected additivity rule, total, elastic and inelastic cross sections including dipole interactions were calculated (1eV - 10keV) in order to complement the experimental data. Elastic differential cross sections were also obtained. An empirical approximation to the inelastic angular distributions based on differential cross sections is proposed. The available integral and differential cross sections and energy loss distributions in the range 1 eV - 10 keV are combined into a table of recommended electron interaction cross sections with THF.Peer Reviewe