Theoretical study on positron scattering by benzene over a broad energy range

Abstract

In this paper two theoretical methodologies, the Schwinger multichannel (SMC) method and the independent atom model with the screening corrected additivity rule (IAM-SCAR), were employed to study positron scattering by benzene over a broad impact energy range. The SMC calculations were carried out in the static plus polarization approximation, accounting for the elastic channel, for impact energies up to 20 eV. The IAM-SCAR method covered energies up to 1000 eV to provide total, elastic, ionization, excitation, and positronium formation cross sections. In the low-energy region we discuss how the description of the polarization effects affects the cross sections. In particular, our calculations support the existence of a bound state in the positron scattering by benzene, in agreement with previous predictions by Young and Surko [Phys. Rev. A 77, 052704 (2008)].

Elastic Scattering of Slow Positrons by Pyrazine

“…In this panel we also compare the present cross sections with results for pyrimidine and benzene, both obtained with the SMC method. 19,20 The results obtained with the SP3 scheme agree well in shape and magnitude with benzene, and is lower than the cross section of pyrimidine as expected, because of the dipole moment of this molecule. It is worth mentioning that for benzene, the elastic results obtained with the independent atom model with screening-corrected additivity rule (IAM-SCAR) 20 and with model potential calculations by Occhigrossi and Gianturco, 26 agree well with the SMC results, 20 while the "enhanced" R-matrix results obtained by Franz and Franz 27 are bigger.…”

“…Differential cross sections for elastic positron collision with pyrazine at 1, 2, 3, 4, 5, and 6 eV. We compared our present results with available results for benzene calculated by Barbosa et al20 and pyrazine calculated by Barbosa et al19 and measured by Palihawadana et al18 The Journal of Physical Chemistry A…”

“…This can be explained by the long-range part of the polarization potential being better described by the SP3 scheme. We also show in this figure, for purposes of comparison, the experimental DCSs of Palihawadana et al for pyrimidine and calculated DCSs of Barbosa et al for pyrimidine and benzene molecules. The data of Palihawadana et al are folded, meaning that they include contributions for DCS­(θ) + DCS­(180° – θ) with θ ranging from 0° to 90°.…”

“…Upper panel: SP1 (dashed red line), SP2 (dashed-dotted-dotted blue line), and SP3 (solid green line). In the work of Barbosa et al, the dotted magenta line and dotted dash black line show the results of elastic SMC calculations from pyrimidine and benzene, respectively. Lower panel: SP3 cross section for pyrazine (solid green line), experimental measurements from pyrimidine: quasi-elastic cross section of Palihawadana et al: yellow triangle up; TCS of Zecca et al: magenta circle.…”

First-Principles Study on Electron-Induced Excitations of Atomic Layer Deposition Precursors: Inelastic Electron Wave Packet Scattering with Cobalt Tricarbonyl Nitrosyl Co(CO)3NO Using Time-Dependent Density Functional Theory

“…In spite of the importance of understanding the atomic and excited electronic processes during the EE reactions and other related applications, there have been limited theoretical investigations, especially in a quantitative manner. Several well-known theoretical techniques being developed for investigating the cross-sections of collision events, including the Independent Atom Model with Additivity Rule (IAM-SCAR) and the Spherical Complex Optical Potential (SCOP) methods. − These methods are capable of calculating relatively accurate cross-sections of electron scattering. In addition to the cross-sections, as for the issues of electron-enhanced reactions, the energy transferred from the impinging electron to the target and the corresponding electron excitations in molecules or ligands by electron impact can provide quantitatively essential information for uncovering the underlying mechanisms of electron-induced chemical reaction processes.…”