Minaxi Vinodkumar

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.

Electron impact total ionization cross sections for atoms with Z = 49-54

Spherical complex optical potential formalism and complex scattering potential–ionization contribution are used to generate electron impact total inelastic and total ionization cross section, respectively, for the atoms In, Sn, Sb, Te, I and Xe. Roothaan–Hartree–Fock calculations are used to approximate the atomic orbital wavefunction and hence to model the target charge densities and static potentials for these atoms. The results for the above targets are presented for energies ranging from ionization threshold to 2000 eV. Graphs are plotted with other theories and measurements wherever available. We have obtained a systematic and uniform result with an overall agreement with other data for all the elements presented here.

Electron impact total cross section for acetylene over an extensive range of impact energies (1 eV-5000 eV)

Comprehensive study on electron impact for acetylene molecule is performed in terms of eigenphase diagram, electronic excitation cross sections as well as total cross section calculations from 1 eV to 5000 eV in this article. Computation of cross section over such a wide range of energy is reported for the first time. We have employed two distinct formalisms to derive cross sections in these impact energies. From 1 eV to ionization threshold of the target we have used the ab initio R-matrix method and then spherical complex optical potential method beyond that. At the crossing point of energy, both theories matched quite well and hence prove that they are consistent with each other. The results presented here expectedly give excellent agreement with other experimental values and theories available. The techniques employed here are well established and can be used to predict cross sections for other targets where data are scarce or not available. Also, this methodology may be integrated to online database such as Virtual Atomic and Molecular Data Centre to provide cross section data required by any user.

Screening-corrected electron impact total and ionization cross sections for boron trifluoride (BF3) and boron trichloride (BCl3)

In this paper, we report modified calculations for total elastic, total ionization and total (complete) cross sections for boron trifluoride (BF3) and boron trichloride (BCl3) upon electron impact at energies from around threshold to 2000 eV. We have proposed a model which allows screening correction due to the overlapping of atoms as seen by incident electrons in a complex molecule. We have employed the well-known spherical complex optical potential (SCOP) formalism to evaluate total elastic and total inelastic cross sections and hence total (complete) cross sections. The ionization cross sections were derived using the complex optical potential–ionization contribution (CSP-ic) method developed by us. The present results are compared with available experimental and other theoretical data wherever available and overall good agreement is observed. The present screening-corrected model shows improvement over the previous method especially at low energies. We also predict total elastic cross sections for these targets using this method.

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 impact total cross section calculations for CH3SH (methanethiol) from threshold to 5 keV

We report calculated total elastic cross sections Qel, total ionisation cross sections, Qion, summed total excitation cross sections ∑Qexc and total cross sections QT for CH3SH upon electron impact for energies from ionisation threshold to 5 keV. We have employed Spherical Complex Optical Potential (SCOP) formalism to calculate total elastic cross section Qel, and total inelastic cross section Qinel and used Complex Scattering Potential – the ionisation contribution (CSP-ic) method to extract the ionisation cross sections, Qion, from the calculated Qinel. The calculated total cross sections are examined as functions of incident electron energy and are compared with available data wherever possible and overall good agreement is observed. In this work Qel, Qion, and ∑Qexc are reported for the first time for CH3SH in this energy range.

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.

Electron induced chemistry of thiophene

A comprehensive theoretical study of electron scattering with thiophene over a wide impact energy range is reported in this article. Total, elastic, differential and momentum transfer cross sections were computed at low energy using an ab initio R-matrix method through QUANTEMOL-N. The R-matrix calculations were carried out using the Complete Active Space–Configuration Integration (CAS–CI) method employing Static Exchange (SE) and Static Exchange plus Polarization (SEP) models. Beyond the ionization threshold, from intermediate to high energy the calculations were carried out using the Spherical Complex Optical Potential (SCOP) formalism. There is a smooth crossover of the two formalisms at the overlap energy, and hence we are able to predict the cross sections over a wide energy range. Apart from the scattering cross section calculations, the other focus was to obtain resonances which are important features at low energy. We observed three prominent structures in the total cross section (TCS) curve. The first peak at 2.5 eV corresponds to the formation of a σ* resonance which is attributed to a Feshbach resonance, in good agreement with earlier predicted experimental and theoretical values of 2.65 eV and 2.82 eV, respectively. The second peak observed at 4.77 eV corresponds to the shape resonance that resembles earlier predicted experimental values of 5 eV and 5.1 eV, which is attributed to ring rupture. The third peak at 8.06 eV is attributed to a core excited shape resonance. There is a lone previous theoretical dataset for the total cross section by da Costa et al. [R. F. da Costa, M. T. do N. Varella, M. Lima, and M. Bettega, 2013, J. Chem. Phys., 138, 194306] from 0 to 6 eV, and no other theoretical or experimental work is reported at low energy to the best of our knowledge. Hence the present work is important to fill the void of scattering data as the earlier work is fragmentary. The differential, momentum transfer and excitation cross sections beyond 6 eV are reported for the first time.

Electron-impact total cross sections for inelastic processes for furan, tetrahydrofuran and 2,5-dimethylfuran

We report total inelastic, total ionisation and summed total excitation cross sections for electron scattering on furan, tetrahydrofuran (THF) and 2,5-dimethylfuran at energies between the ionisation threshold and 5 keV. We have employed the spherical complex optical potential formalism (SCOP) to calculate the total inelastic cross sections (Qinel) and have used complex scattering potential-ionisation contribution (CSP-ic) method to derive total ionisation cross sections (Qion) and summed total excitation cross sections (∑Qexc) from the calculated Qinel. We have also computed Qion for these molecules using binary-encounter-Bethe (BEB) approach. We have compared our total cross sections (TCS) with available experimental as well as previous theoretical results and have found good agreement. The results are presented graphically as well as numerically.