Experimental and theoretical cross sections for positron scattering from the pentane isomers

10 págs.; 8 figs.; 3 tabs.Isomerism is ubiquitous in chemistry, physics, and biology. In atomic and molecular physics, in particular, isomer effects are well known in electron-impact phenomena; however, very little is known for positron collisions. Here we report on a set of experimental and theoretical cross sections for low-energy positron scattering from the three structural isomers of pentane: normal-pentane, isopentane, and neopentane. Total cross sections for positron scattering from normal-pentane and isopentane were measured at the University of Trento at incident energies between 0.1 and 50 eV. Calculations of the total cross sections, integral cross sections for elastic scattering, positronium formation, and electronic excitations plus direct ionization, as well as elastic differential cross sections were computed for all three isomers between 1 and 1000 eV using the independent atom model with screening corrected additivity rule. No definitive evidence of a significant isomer effect in positron scattering from the pentane isomers appears to be present. ©2016 AIP Publishing LLCG.G. and F.B. would like to acknowledge the Spanish Ministerio de Economía y Productividad (Project No. FIS2012-31230) and the European Science Foundation (COST Action Grants Nos. MP1002–Nano-IBCT and MC1301-CELINA) for financial support. Finally, L.C. thanks the Japan Society for the Promotion of Science for his fellowship.Peer Reviewe

Transport properties of electron swarms in tetrahydrofuran under the influence of an applied electric field

10 págs.; 14 figs.; PACS number(s): 34.80.−iUsing an almost complete set of electron impact cross sections for scattering from the important biomolecule tetrahydrofuran (THF), compiled as a part of this study, swarm transport coefficients are determined by solving the Boltzmann's equation over the range of applied reduced fields from 0.01 to 10 000 Td. The present investigation highlights the experimental issues associated with, and the real need for, measurements of the corresponding THF transport coefficients, so that the self-consistency of our proposed cross section set might be evaluated. © 2013 American Physical Society.theAustralian Academy of Science through its European Scientific Exchange Program, and the Spanish Ministerio de Economia y Productividad (Project FIS2012-32320). The experimental part was supported by Project No. PAPIIT IN 111611.Peer Reviewe

Electron impact cross-sections for biomolecules ¿ completeness and selfconsistency via swarm analysis

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/The accuracy and completeness of electron impact cross-sections in water and tetrahydrofuran are assessed through comparison with experimental electron transport coefficients using the pulsed Townsend experiment.Peer Reviewe

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

Integral elastic, electronic-state, ionization, and total cross sections for electron scattering with furfural

8 págs.; 2 figs.; 2 tabs.We report absolute experimental integral cross sections (ICSs) for electron impact excitation of bands of electronic-states in furfural, for incident electron energies in the range 20-250 eV. Wherever possible, those results are compared to corresponding excitation cross sections in the structurally similar species furan, as previously reported by da Costa et al. [Phys. Rev. A 85, 062706 (2012)] and Regeta and Allan [Phys. Rev. A 91, 012707 (2015)]. Generally, very good agreement is found. In addition, ICSs calculated with our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arise due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section for electron-furfural scattering. Where possible, those calculated IAM-SCAR+I ICS results are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, but only for the band I and band II excited electronic states, we also present results from our Schwinger multichannel method with pseudopotentials calculations. Those results are found to be in good qualitative accord with the present experimental ICSs. Finally, with a view to assembling a complete cross section data base for furfural, some binary-encounter-Bethe-level total ionization cross sections for this collision system are presented.D.B.J. thanks the Australian Research Council (ARC) for financial support provided through a Discovery Early Career Research Award, while M.J.B. also thanks the ARC for their support. M.J.B. acknowledges the Brazilian agency CNPq for his “Special Visiting Professor” position at the Federal University of Juiz de Fora. G.G. acknowledges partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230) and the European Union COST Action No. CM1301 (CELINA). Finally R.F.C., M.T.doN.V, M.H.F.B, and M.A.P.L. also acknowledge support from CNPq, while M.T.doN.V. thanks FAPESPPeer Reviewe

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

Elastic Differential Cross Sctions for Electron Collisions with Polyatomic Molecules

Experimental data for electron-polyatomic molecule collisions are reviewed in connection with fusion and processing plasmas, as well as with the associated environmental issues. The electron scattering experiments for differential cross section (DCS) measurements for various processes, such as elastic scattering, have been performed across a broad range of energies (1-100 eV), mainly, at Sophia University since 1978, and some done under the collaborations with the Australian National University, Flinders University, and the Chungnam National University. As a benchmark cross section, elastic DCS are essential for the absolute scale conversion of inelastic DCS, as well as for testing computational methods. The need for cross-section data for a wide variety of molecular 2 species is also discussed, because there is an urgent need to develop an international program to provide the scientific and technological communities with authoritative cross sections for electron-molecule interactions. Note that the detailed comparison with other data available is not given here. Ruther, other available data can be found in the references we cite. This course of action was adopted to keep this report to a sensible length, so that only our numerical data is provided here

An improved set of electron-THFA cross sections refined through a neural network-based analysis of swarm data

We review experimental and theoretical cross sections for electron transport in α-tetrahydrofurfuryl alcohol (THFA) and, in doing so, propose a plausible complete set. To assess the accuracy and self-consistency of our proposed set, we use the pulsed-Townsend technique to measure drift velocities, longitudinal diffusion coefficients, and effective Townsend first ionization coefficients for electron swarms in admixtures of THFA in argon, across a range of density-reduced electric fields from 1 to 450 Td. These measurements are then compared to simulated values derived from our proposed set using a multi-term solution of Boltzmann’s equation. We observe discrepancies between the simulation and experiment, which we attempt to address by employing a neural network model that is trained to solve the inverse swarm problem of unfolding the cross sections underpinning our experimental swarm measurements. What results from our neural network-based analysis is a refined set of electron-THFA cross sections, which we confirm is of higher consistency with our swarm measurements than that which we initially proposed. We also use our database to calculate electron transport coefficients in pure THFA across a range of reduced electric fields from 0.001 to 10000 Td

Electron impact ionization of 1-propanol

Experimental measurements of the cations created in electron impact ionization have been undertaken for the primary isomer of propanol using a Hidden Quadrupole Mass Spectrometer (EPIC 300), with a mass resolution of 1 amu. The mass spectra recorded at an incident electron energy of 70 eV reveals the relative probability of forming 50 different cations, by either direct ionization or dissociative ionization. Individual partial ionization cross sections (PICS) for 31 different cations were measured for the first time in this work, for the incident electron energy range from 10 to 100eV. Also, appearance energies (AEs) and Wannier exponents for the 16 most intense cations formed in electron collisions with 1-propanol are reported. Where possible, those results are compared to those from an earlier investigation. Total Ionization Cross Sections (TICS) were also obtained from the sum of the measured PICS, for nearly all cations measured, and are compared to relevant data reported in the literature. In addition, as a part of this study, theoretical TICS were calculated using the Binary-encounter Bethe (BEB) and independent atom model with screening corrected additivity rule (IAM - SCAR) methods. Good agreement between current measured and calculated TICSs and corresponding earlier results was typically found