K. N. Joshipura

Electron impact total cross sections of CHx ,N H x and OH radicals vis-` a-vis their parent molecules

Various total cross sections for the impact of electrons on free radicals CHx ,N Hx and OH are calculated at intermediate to high energies. The known ionization data on the parent molecules CH4 ,N H 3 and H2O are employed to extract total ionization cross sections of the respective radicals using total inelastic cross sections, which we have calculated through a complex optical potential. The results give an upper bound of the total ionization cross section in the energy region around 100 eV, and are in suitable harmony with available experimental data at higher energies.

Calculations of elastic, ionization and total cross sections for inert gases upon electron impact: threshold to 2 keV

In this paper we report comprehensive calculations of total elastic (Qel), total ionization (Qion) and total (complete) cross sections (QT) for the impact of electrons on inert gases (He, Ne, Ar, Kr and Xe) at energies from about threshold to 2000 eV. We have employed the spherical complex optical potential (SCOP) formalism to evaluate Qel and QT and used the complex spherical potential-ionization contribution (CSP-ic) method to derive Qion. The dependence of QT on polarizability and incident energy is presented for these targets through an analytical formula. Mutual comparison of various cross sections is provided to show their relative contribution to the total cross sections QT. Comparison of QT for all these targets is carried out to present a general theoretical picture of collision processes. The present calculations also provide information, hitherto sparse, on the excitation processes of these atomic targets. These results are compared with available experimental and other theoretical data and overall good agreement is observed.

Total electron scattering cross sections for NO, CO, , , and eV)

Various total cross sections for electron scattering on the heteronuclear molecules NO, CO, and are calculated at energies from 50 eV onwards. The approximate additivity rule used earlier has been modified by separating - molecule interactions into short-range and long-range parts. The resulting modified additivity rule for - molecule cross sections is simple but more effective and it yields better accord with experiments, especially above 100 eV incident energy.

Total and ionization cross sections of electron scattering by fluorocarbons

Electron impact total cross sections (50–2000 eV) and total ionization cross sections (threshold to 2000 eV) are calculated for typical plasma etching molecules CF4, C2F4, C2F6, C3F8 and CF3I and the CFx (x = 1–3) radicals. The total elastic and inelastic cross sections are determined in the spherical complex potential formalism. The sum of the two gives the total cross section and the total inelastic cross section is used to calculate the total ionization cross sections. The present total and ionization cross sections are found to be consistent with other theories and experimental measurements, where they exist. Our total cross section results for CFx (x = 1–3) radicals presented here are first estimates on these species.

Electron impact total (elastic + inelastic) cross-sections of C, N & O atoms and their simple molecules

Total (elastic + inelastic) cross-sections for electron scattering from C, N, O atoms and their simple molecules are studied theoretically. Thee−-C, N, O atomic calculations are done in the complex optical potential approach. To study the electron scattering from O2, N2, CO, NO, CN, C2 as well as CO2, N2O, NO2 O3 targets, we have adopted an additivity rule, wherein the molecular cross-section is an incoherent sum of the cross-sections of the constituent atoms. The cross-sections of C, N & O atoms are presented at incident energiesEi=10–1000 eV, the molecular cross-sections are presented atEi=100–1000 eV. The reliability of the additivity rule is discussed against the background of experimental data.

ELECTRON SCATTERING CROSS SECTIONS WITH HF, OH, NH AND CH MOLECULES

Abstract Total cross sections including elastic scattering, electronic excitation-ionisation and the dipole rotational excitation are calculated for electron impact on HF, OH, NH, and CH molecules. The additivity rules as well as single-centre expansion are employed for this purpose. A comparison was possible for the e-HF system only. Our results are expected to be good at intermediate to high energies (> 50 eV).

Various total cross-sections for electron impact on \(\), \(\) and \(\)\(\)

Abstract:Cross-sections for the impact of electrons having energy Ei =50 - 5000 eV are evaluated for polyatomic molecules , , , , and . Total (complete) cross-sections and total inelastic cross-sections are calculated for these targets by employing the atomic optical potentials and additivity rules. A variant of our previous work, to be called MAR-SC has been developed for molecules such as the present ones, where two approximately independent scattering centres can be identified. We find a good general accord of our theoretical values with various experimental data. Also given presently is an analytical fit , incorporating polarizability , for the high energy total cross-sections for 18-electron targets. Tentative upper and lower limits for the electron molecule total ionization cross-sections are identified and a break-up into elastic and inelastic contributions is exhibited.

Electron collisions with sulfur compounds SO, SO2 and SO2AB (A, B = Cl, F): various total cross sections

This paper reports our theoretical investigations into electron scattering with SO, SO2, SO2Cl2, SO2ClF and SO2F2 in the energy range from the ionization threshold to 2000 eV. The present studies are prompted by the occurrence and applications of these molecular species in atmospheric and astrophysical systems, together with a paucity of data for SO and SO2AB (A, B = Cl, F) species. Complex model potential calculations are carried out to find total elastic as well as inelastic cross sections, and ionization cross sections are retrieved from inelastic cross sections in a semi-empirical approximation. Comparisons with other data are made and discussed.

R-matrix calculation of low-energy electron collisions with LiH

Calculations are performed for electron scattering from LiH. These show that use of a close-coupled expansion gives results significantly different from calculations performed at the static exchange level employed in all previous calculations. In particular the close-coupled calculations find a Feshbach resonance which follows the first excited, a3Σ−, state curve. This resonance could provide a route to dissociative attachment and electron impact vibrational excitation. Elastic scattering cross sections, which are very large, as well as inelastic cross sections for excitation to the four lowest electronically excited states are presented as a function of LiH bond length.

Electron impact ionization of H2O molecule in crystalline ice

Abstract The present work focuses on electron impact scattering in crystalline ice, which is an exotic solid. The major difference between crystalline form and amorphous form lies in its structure. Here we consider the H2O molecule to possess properties consistent with the ice structure. Our basic calculation rests on the complex optical potential for the e-molecule system, with the molecular charge density as an input. To examine a single scattering event in condensed phases, we build up a model scattering potential to determine total inelastic cross-section Qinel. Finally an estimate of the total ionization cross-section, Qion for H2O (free), H2O (amorphous) and H2O (ice) in the energy range from threshold to 2000 eV, is obtained through semi-empirical arguments.