Showing papers by "Bobby Antony published in 2020"

A Decade with VAMDC: Results and Ambitions

Abstract: This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of the VAMDC e-infrastructure. We analyse the past 10 years of VAMDC development and operation, and assess their impact both on the field of atomic and molecular (A&M) physics itself and on heterogeneous data management in international cooperation. The highly sophisticated VAMDC infrastructure and the related databases developed over this long term make them a perfect resource of sustainable data for future applications in many fields of research. However, we also discuss the current limitations that prevent VAMDC from becoming the main publishing platform and the main source of A&M data for user communities, and present possible solutions under investigation by the consortium. Several user application examples are presented, illustrating the benefits of VAMDC in current research applications, which often need the A&M data from more than one database. Finally, we present our vision for the future of VAMDC.

Positron Scattering from Atoms and Molecules

Abstract: 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.

Positron Scattering from Pyridine and Pyrimidine

Abstract: Positron impact scattering cross-sections for pyridine and pyrimidine are reported here. Spherical complex optical potential formalism is used to calculate the positronium formation, elastic, total...

Ionization cross sections for plasma relevant molecules

Abstract: We have chosen five complex molecules ($C_3F_6O$, $C_4F_8O$, $C_5F_{10}O$, $C_6F_{12}O$ and $C_4F_7N$) for the present investigation, which are considered as potential substitute for $SF_6$ in plasma applications. There are some theoretical data available for ionisation cross section with contradicting values, especially at peak. To the best of our knowledge, no experimental data is found in the literature to validate previous calculations. In this work, we have efficiently included \hl{nuclear charge distribution and the corresponding electrostatic potential} in the spherical complex optical potential formalism for the first time. Thus, the nuclear static effect is included in the calculation of inelastic cross section of these plasma relevant molecules by electron scattering. Complex scattering potential-ionisation contribution method is used to derive the ionisation cross section. We have done a test run of the adopted changes on targets for which experimental measurements are available. Excellent agreement can be found for the entire energy range. For present plasma relevant molecules, notable difference is seen in the lower energy region of investigation, which is a major improvement in our calculation. However, beyond the peak, the values are consistent with previous method. For $C_6F_{12}O$ this is the first report of ionisation cross section.

Electron Scattering Cross Sections for Anthracene and Pyrene

Abstract: UK molecular R-matrix calculations have been carried out for electron scattering from anthracene and pyrene. These molecules belong to the family of polycyclic hydrocarbons (PAHs) and are found in ...

Electron scattering studies of BF and BF 2

Abstract: The present article reports calculated elastic, differential, momentum transfer and excitation cross section for electron scattering from BF and BF_{2} radicals using the ab initio R-matrix method. The calculations are performed with complete active space—configuration interaction and static exchange models for both targets to yield scattering cross sections and resonance parameters. Elastic and momentum transfer cross sections are also calculated using the spherical complex optical potential method to cover a wide energy range. The total ionization cross section is also reported from ionization threshold to 5 keV. The calculated cross sections for these neutral species are important for BF_{3} plasma and are reported for the first time to the best of our knowledge except ionization.

Low-Energy Electron Scattering from Dimethyl Ether.

Abstract: Low-energy (0.1 to 15 eV) R-matrix calculation is performed for dimethyl ether molecule. Electronic excitation and momentum transfer cross section for low energies are reported for the first time. Present differential cross sections show good agreement with previous data in terms of shape but are significantly higher in magnitude. Apart from low energies, we have also performed high-energy calculation (11-5000 eV) using spherical complex optical potential formalism. To deal with the molecular nature of the present target, we have applied an effective potential method in our computation for the first time. Good consistency can be seen at the overlapping energies of the two calculations.

Electron induced scattering cross section for pyrrole and its isomers

Abstract: Elastic, ionization and total cross section for electron scattering from pyrrole and its isomers, viz. 2H-pyrrole, 3H-pyrrole, cycloprapanecarbonitrile, E-2 butenenitrile and Z-2 butenenitrile are reported in this article. These cross sections are calculated using the spherical complex optical potential formalism and the complex scattering potential-ionization contribution method in the energy range from the ionization threshold of the molecule to 5 keV. The geometric screening correction is used to reduce the overestimation of cross section due to overlap in charge distribution among atoms or group of atoms in the molecule. The isomeric effect through cross section values are also investigated in this work. The cross section data reported in this paper are key input for modeling Titan’s atmosphere due to the presence of pyrroles and abundant electrons in its medium.