scholarly journals Electronic excitation of atoms by positron impact using the scaling Born approach

2018 ◽  
Vol 64 (6) ◽  
pp. 598
Author(s):  
AOE Lino
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Cross Sections ◽  
Electronic Excitation ◽  
Simple Procedure ◽  
Electronic States ◽  
Impact Excitation ◽  
Positron Impact

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.

scholarly journals Electronic excitation of C6H6 by positron impact

2021 ◽  
Vol 67 (2 Mar-Apr) ◽  
pp. 188
Author(s):  
J. L. S. Lino
Keyword(s):  
Electron Scattering ◽  
Cross Sections ◽  
Electronic Excitation ◽  
Theoretical Calculations ◽  
Electronic States ◽  
Incident Particle ◽  
Positron Impact ◽  
Time Integral ◽  
First Time ◽  
Inelastic Processes

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

Effective Oscillator Strengths of Neon from Electron Impact Excitation

1975 ◽  
Vol 53 (9) ◽  
pp. 850-853 ◽  
Author(s):  
D. Roy ◽  
J.-D. Carette
Keyword(s):  
Experimental Data ◽  
Electron Impact ◽  
Cross Sections ◽  
Electronic States ◽  
Oscillator Strengths ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Excitation Cross Sections ◽  
Relative Excitation ◽  
Good Agreement

From experimental data about relative excitation cross sections of many electronic states of neon, the effective oscillator strengths of these transitions have been computed. There is a good agreement between these results and the single available value of optical oscillator strength.

scholarly journals Relativistic B-Spline R-Matrix Calculations for Electron Collisions with Ytterbium

Atoms ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 47
Author(s):  
Kathryn R. Hamilton ◽  
Klaus Bartschat ◽  
Oleg Zatsarinny
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Cross Sections ◽  
Matrix Method ◽  
Model Potential ◽  
Electron Collisions ◽  
R Matrix ◽  
B Spline ◽  
Potential Approach

We have applied the full-relativistic Dirac B-Spline R-matrix method to obtain cross sections for electron scattering from ytterbium atoms. The results are compared with those obtained from a semi-relativistic (Breit-Pauli) model-potential approach and the few available experimental data.

K-, L-, and M-shell ionization of atoms by electron and positron impact

1996 ◽  
Vol 74 (7-8) ◽  
pp. 376-383 ◽  
Author(s):  
S. P. Khare ◽  
J. M. Wadehra
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Positron Impact ◽  
Electrons And Positrons ◽  
Virtual Photons ◽  
Plane Wave Born Approximation ◽  
Ionization Cross Sections ◽  
Impact Energies ◽  
Shell Ionization ◽  
Good Agreement

The plane-wave Born approximation with Coulomb, relativistic, and exchange corrections is employed to obtain the K-, L1-, L2-, L3-, and M-shell ionization cross sections of a number of atoms bombarded by electrons and positrons in the energy range varying from the threshold of ionization to 1 GeV. Transverse interaction of virtual photons with atoms is also included and it is found to be of great significance for impact energies greater than about 1 MeV. For K- and L-shell ionization, good agreement between the theoretical values and various experimental data for electron-impact cross sections is obtained. However, for the M shell, the theory overestimates the experimental cross sections. For positron impact the agreement between the present results and the limited experimental data is found to be quite satisfactory.

scholarly journals Positron Scattering from Atoms and Molecules

Atoms ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 29 ◽  
Author(s):  
Sultana N. Nahar ◽  
Bobby Antony
Keyword(s):  
Cross Section ◽  
Electron Scattering ◽  
Cross Sections ◽  
Optical Potential ◽  
Inert Gases ◽  
Positron Impact ◽  
Positron Scattering ◽  
Atoms And Molecules ◽  
Section Data ◽  
Theoretical Approaches

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.

scholarly journals Deconvolution of Overlapping Features in Electron Energy-loss Spectra: Determination of Absolute Differential Cross Sections for Electron-impact Excitation of Electronic States of Molecules

1997 ◽  
Vol 50 (3) ◽  
pp. 525 ◽  
Author(s):  
L. Campbell ◽  
P. J. O. Teubner ◽  
M. J. Brunger ◽  
B. Mojarrabi ◽  
D. C. Cartwright
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Cross Sections ◽  
Differential Cross ◽  
Electronic States ◽  
Impact Excitation ◽  
Spectroscopic Constants ◽  
Differential Cross Sections ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

A set of three computer programs is reported which allow for the deconvolution of overlapping molecular electronic state structure in electron energy-loss spectra, even in highly perturbed systems. This procedure enables extraction of absolute differential cross sections for electron-impact excitation of electronic states of diatomic molecules from electron energy-loss spectra. The first code in the sequence uses the Rydberg–Klein–Rees procedure to generate potential energy curves from spectroscopic constants, and the second calculates Franck–Condon factors by numerical solution of the Schrödinger equation, given the potential energy curves. The third, given these Franck–Condon factors, the previously calculated relevant energies for the vibrational levels of the respective electronic states (relative to the v″ = 0 level of the ground electronic state) and the experimental energy-loss spectra, extracts the differential cross sections for each state. Each program can be run independently, or the three can run in sequence to determine these cross sections from the spectroscopic constants and the experimental energy-loss spectra. The application of these programs to the specific case of electron scattering from nitric oxide (NO) is demonstrated.

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