Biplab Goswami

Electron induced chemistry of disilane

Theoretical study of electron impact scattering by disilane molecule is reported in this article. Total, elastic, excitation and differential cross sections were computed at low incident energies using the R-matrix method through QUANTEMOL-N. The total cross section calculation was extended to higher energies using spherical complex optical potential formalism. The smooth transition at the overlap of two formalisms around the ionization threshold of the target has helped to predict cross sections over a wide energy range from 0.1 eV to 5 keV. The resonance position predicted by the present static exchange and static exchange plus polarization models at 3.3 and 3.0 eV respectively agrees quite well with previous theoretical and experimental results. The inclusion of polarization effects in the calculation has considerably improved the position of the resonance from the previous static exchange calculation. In general the results obtained for total, elastic and differential cross sections show reasonable agreement with the experiment. The excitation cross section of disilane from ground state to various excited states is reported for the first time.

Calculations of electron collision and ionisation of rare gas dimers

Thresholds to 2000 eV electron impact total inelastic cross-sections for rare gas dimers were calculated employing a spherical complex optical potential formalism. From these inelastic cross-sections, total ionisation cross-sections are derived by applying a complex scattering potential-ionisation contribution method. This is a maiden attempt to study the total ionisation cross-section for most of these targets. To the best of our knowledge, no measurements or calculations are available for all the targets in the literature with which we can compare our results. The results show a linear relationship between maximum ionisation cross-section and target radius, depending on its size. Such dependence can confirm the consistency of the data presented here.

Electron scattering from germanium tetrafluoride

This paper describes the use of two methodologies to find the electron impact total cross sections (TCS) for GeF4 molecule from 1–5000 eV. The ab initio R-matrix method is used at low impact energies and the spherical complex optical potential (SCOP) formalism at intermediate to high energies. The TCS from both formalisms match quite well at the overlapping energy (∼12 eV) allowing us to predict the cross section for such a wide energy range. Besides TCS, calculations for electronic excitation, rotational excitation, momentum transfer and differential elastic cross sections are also reported using the R-matrix method. A broad resonant feature at 5.69 eV due to degenerate 2B1, 2B2 and 2B3 states is observed, revealing the probability of anion formation by an electron attachment process and further decay to neutral and negative ion fragments. The electronic and rotational excitation cross sections for e-GeF4 scattering are reported for the first time.

Electron impact scattering by SF6 molecule over an extensive energy range

The present article reports the theoretical total cross sections for e-SF6 scattering over the energy range 0.1–5000 eV. For low-energy calculations up to the ionization threshold of the target, the ab initio R-matrix formalism is employed, and beyond that energy the spherical complex optical potential method is used. Elastic, electronic excitation, rotational excitation, momentum transfer and total cross sections were calculated and the results of the low-energy calculations are presented. Differential elastic cross sections for various energies are also reported here. We have identified and detected two resonances at energies of 5.43 and 17.02 eV with the possible formation of anions. The present results show reasonable agreement with the existing theoretical and experimental results. The current work is the first report of the rotational excitation cross sections for the e-SF6 scattering system.

Electron Impact Total Ionization Cross Sections for Plasma Wall Coating Elements

The interaction of electrons with plasma walls has been a topic of great interest in modeling the plasma for fusion reactors. The selection of a suitable plasma wall coating element is critical in the design of reactors like the Tokomak. In any plasma model, phenomena like wall erosion, transport of impurities, and redeposition on the walls are vital. Various elements are used as coatings on the plasma walls like Li, Be, B, Ti, and Fe. Hence, in this article we have presented a method for calculating the total ionization cross section for these elements. The cross sections are calculated in the energy range from the ionization threshold to 2 keV. The results obtained are found to be consistent and agree well with other measurements and theories wherever available.