scholarly journals Electronic excitation of C6H6 by positron impact

2021 ◽  
Vol 67 (2 Mar-Apr) ◽  
pp. 188
Author(s):  
J. L. S. Lino

Experiments on electronic excitation of molecules using positron as incident particle have shown much larger cross sections than in the electron scattering case.  The comprehension of these inelastic processes represent a great challenge and only few studies on electronic excitation of molecules are discussed in the literature. For example, for the C6H6 molecule experimental and theoretical calculations are not in a very advanced state same for electron scattering case (Benzene represent a simplest aromatic hydrocarbon and very important chemical compound due to its role as a key precursor in process pharmaceutical). Recent experiments on electronic excitation of C6H6 (1B1u, and 1E1u electronic states) using electron as incident particle are available by Kato et al (J.Chem.Phys.134 134308(2011)). Motivated by their experiments we have taken up the task to investigate the same electronic excitation of C6H6 using positron as incident particle.  For the first time, integral cross sections in e+ - C6H6 (1B1u, and 1E1u electronic states) using the scaling Born positron (SBP) approach are reported and in the absence of the experimental data and developments theoretical, comparisons are made with analogous electron scattering.Keywords: Born, positron, scaling

2018 ◽  
Vol 64 (6) ◽  
pp. 598
Author(s):  
AOE Lino

We consider the efficacy of the scaling Born positron (SBP) approach, in calculating reliable integral cross sections (ICS) for positron impact excitation of electronic states in atoms. We will demonstrate, using specific examples as H, He, Hg, and Mg, that this relatively simple procedure can generate quite accurate ICS when compared with more sophisticated methods. In the absence of the experimental data, comparisons are made with analogous electron scattering.


Atoms ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 29 ◽  
Author(s):  
Sultana N. Nahar ◽  
Bobby Antony

A review on the positron scattering from atoms and molecules is presented in this article. The focus on positron scattering studies is on the rise due to their presence in various fields and application of cross section data in such environments. Positron scattering is usually investigated using theoretical approaches that are similar to those for electron scattering, being its anti-particle. However, most experimental or theoretical studies are limited to the investigation of electron and positron scattering from inert gases, single electron systems and simple or symmetric molecules. Optical potential and polarized orbital approaches are the widely used methods for investigating positron scattering from atoms. Close coupling approach has also been used for scattering from atoms, but for lighter targets with low energy projectiles. The theoretical approaches have been quite successful in predicting cross sections and agree reasonably well with experimental measurements. The comparison is generally good for electrons for both elastic and inelastic scatterings cross sections, while spin polarization has been critical due to its sensitive perturbing interaction. Positron scattering cross sections show relatively less features than that of electron scattering. The features of positron impact elastic scattering have been consistent with experiment, while total cross section requires significant improvement. For scattering from molecules, utilization of both spherical complex optical potential and R-matrix methods have proved to be efficient in predicting cross sections in their respective energy ranges. The results obtained shows reasonable comparison with most of the existing data, wherever available. In the present article we illustrate these findings with a list of comprehensive references to data sources, albeit not exhaustive.


2021 ◽  
Vol 129 (12) ◽  
pp. 1471
Author(s):  
И.В. Чернышова ◽  
Е.Э. Контрош ◽  
О.Б. Шпеник

Abstract– The interactions of low-energy electrons (<20 eV) with D-ribose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of D-ribose molecules occurs effectively even at an electron energy close to zero. as well as in the energy range 5.50–9.50 eV. In the total cross section of electron scattering by molecules, resonance features at energies of 5.00–9.00 eV in the region of formation of ionic fragments C3H4O2–, C2H3O2–, OH–, associated with the destruction of molecular heterocycles, were experimentally discovered for the first time. The correlation of the features observed in the scattering and dissociative electron attachment cross sections is analyzed.


1997 ◽  
Vol 50 (3) ◽  
pp. 473 ◽  
Author(s):  
Robert K. Nesbet

Accurate low-energy electron scattering data are needed in many fields of physics. However, accurate experiments are difficult to design and to carry out. By 1967 low-energy electron–He cross sections had been measured by two different techniques, designed to provide accurate data. Unfortunately, the data differed by amounts well outside the estimated error bars. Despite the relative simplicity of the He atom, decisive theoretical calculations on the e–He system could not be done with methods available in 1967. After a decade of development of theoretical methodology it became possible in 1979 to carry out calculations with absolute estimates of residual error limits. The results were found to agree closely with the momentum transfer cross section deduced from electron swarm data and with recent beam data by improved techniques, but were inconsistent with the original beam data of 1965. More recently, a similar conflict exists between data measured for electron-impact vibrational excitation of the hydrogen molecule by electron swarm and beam techniques. This conflict has persisted despite great progress in beam scattering techniques and in theoretical methods. A brief review of the relevant electron scattering theory will be given.


2020 ◽  
Vol 22 (16) ◽  
pp. 8364-8372
Author(s):  
V. Lemelin ◽  
A. D. Bass ◽  
L. Sanche

We report for the first time the low-energy electron energy loss spectrum for electronic excitation of condensed thymidine measured by high resolution electron energy loss spectroscopy.


Author(s):  
David Stevens ◽  
Tamara Babij ◽  
J R Machacek ◽  
James P Sullivan

Abstract This paper presents measurements of low energy electron scattering from pyridine. The low energy positron beamline at the Australian National University was used for these measurements, with a change in operational parameters allowing for the measurement of electron scattering processes. We have collected data for the low energy total cross section for electron scattering, as well as measurements of the differential cross sections (DCS) for electrons up to 3 eV impact energy. The operation of the beamline will be briefly outlined and data are compared to R-matrix and Schwinger multichannel theoretical calculations, as well as previous experimental data.


Atoms ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 113
Author(s):  
Dibyendu Mahato ◽  
Lalita Sharma ◽  
Rajesh Srivastava

A detailed study of positron impact elastic scattering from methane and silane is carried out using a model potential consisting of static and polarization potentials. The static potential for the molecular target is obtained analytically by using accurate Gaussian molecular wavefunctions. The molecular orbitals are expressed as a linear combination of Gaussian atomic orbitals. Along with the analytically obtained static potential, a correlation polarization potential is also added to construct the model potential. Utilizing the model potential, the Schrödinger equation is solved using the partial wave phase shift analysis method, and the scattering amplitude is obtained in terms of the phase shifts. Thereafter, the differential, integrated and total cross sections are calculated. These cross-section results are compared with the previously reported measurements and theoretical calculations.


2020 ◽  
Vol 21 (4) ◽  
pp. 302-307
Author(s):  
V.O. Zheltonozhsky ◽  
◽  
D.E. Myznikov ◽  
A.M. Savrasov ◽  
V.I. Slisenko

The average cross-sections were measured at the first time for 7Bе population at bremsstrahlung end-point energies 40 and 55 MeV and for the 10B(γ,t)7Bе reaction at bremsstrahlung end-point energy 20 MeV. The theoretical calculations carried out within the framework of the software packages EMPIRE-3.2 and TALYS-1.9 demonstrate the domination of the nonstatistical processes.


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