Calculations of total ionization cross sections for halogen compounds on electron impact from threshold to 2 keV (original) (raw)
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Electron impact total ionization cross sections for halogens and their hydrides
International Journal of Mass Spectrometry, 2010
a b s t r a c t Present paper reports electron impact total ionization cross sections (Q ion ) for all the components of DNA and RNA molecules from threshold to 2000 eV. We have employed spherical complex optical potential (SCOP) formalism to calculate the total inelastic cross sections and have deduced total ionization cross sections using complex scattering potential-ionization contribution (CSP-ic) method. DNA and RNA being the complex molecules, these cross sections are evaluated using the group additivity rule. The present results find good accord with the available previous theoretical estimates. In absence of experimental data for these biomolecules, the present theoretical estimates prove to be the reference data source. Q ion for sugar phosphate backbone of RNA and for complete DNA and RNA units are reported for the first time in this work.
Journal of Physics B-atomic Molecular and Optical Physics, 2010
In this paper we report calculations of the total ionization cross sections, Q ion , for environmentally sensitive molecules, namely CO, CO 2 , CS, OCS, CS 2 and S 2 , upon electron impact for energies from circa threshold to 5000 eV. Spherical complex optical potential (SCOP) formalism is employed to evaluate total inelastic cross sections, Q inel . Total ionization cross sections, Q ion , are extracted from the total inelastic cross sections, using a semi-empirical formalism developed by us, called the 'complex spherical potential-ionization contribution' (CSP-ic) method. The present results are compared with both theoretical and experimental data available in the literature and overall good agreement is observed for all the reported molecules.
The Journal of Physical Chemistry a, 2011
The experimental determination of absolute total electron impact ionization cross-sections for polyatomic molecules has traditionally been a difficult task and restricted to a small range of species. This article reviews the performance of three models to estimate the maximum ionization cross-sections of some 65 polyatomic organic and halocarbon species. Cross-sections for all of the species studied have been measured experimentally using the same instrument, providing a complete data set for comparison with the model predictions. The three models studied are the empirical correlation between maximum ionization cross-section and molecular polarizability, the well-known binary encounter Bethe (BEB) model, and the functional group additivity model. The excellent agreement with experiment found for all three models, provided that calculated electronic structure parameters of suitably high quality are used for the first two, allows the prediction of total electron-impact ionization cross-sections to at least 7% precision for similar molecules that have not been experimentally characterized.
The European Physical Journal D - Atomic, Molecular and Optical Physics, 2003
Total ionization cross-sections of electron impact are calculated for the molecular targets CHx, CFx, SiHx, SiFx (x = 1−4) and CCl4 at incident energies 20-3 000 eV. The calculation is based on Complex Scattering Potential approach, as developed by us recently. This leads to total inelastic cross-sections, from which the total ionization cross-sections are extracted by reasonable physical arguments. Extensive comparisons are made here with the previous theoretical and experimental data. The present results are satisfactory except for the CFx and SiFx (x = 1−3) radicals, for which the experimental data are lower than most of the theories by more than 50%.
Review of Theoretical Approach for Total Ionization Cross Section
This article describes the theoretical models for determination of electron-impact ionization cross-section, which has been applied to atoms, ions, and molecules. The model combines the Bethe theory and binary-encounter theory for electron-impact ionization called the binary-encounter Bethe (BEB) model that use the binding energy and average kinetic energy of each subshell that prescribes differential ionization cross section for that shell and S. P. Khare and co-workers give the new Formalism by combining Bethe and Mott's cross-section known as Jain-Khare Formalism are discussed here. Copy
On the electron impact ionization of silicon and metal containing organic molecules
International Journal of Mass Spectrometry, 2014
Calculation of electron impact total inelastic cross sections for three silicon containing organic molecules (Trimethylsilane, Tetraethoxysilane and Hexamethyldisiloxane) and three organometallic complexes (Cyclopentadienyltrimethyl-platinium, Bismethylcyclopentadienyl-ferrum and Bismethylcyclopentadienyl-ruthenium) were performed employing spherical complex optical potential formalism. The complex scattering potential ionization contribution method was then used to derive total ionization cross sections from inelastic cross sections for these targets. The results presented here are for the incident electron energy ranging from ionization threshold to 2000 eV. The comparison with existing measurement shows promising results.
The journal of physical chemistry. A, 2016
In this work, we present and analyze in detail new and recent ionization cross section and mass spectrum determinations, collected in the case of He*, Ne*-H2O, -H2S, and -NH3 ionizing collisions. These sets of data, obtained under the same experimental conditions, are relevant to identify differences in the autoionization stereodynamics of the three hydrogenated molecules and on the selective role of the imaginary part of the optical potential. We demonstrate that in these autoionization processes hydrogen and halogen bonds are competing because they are controlling both real and imaginary components of the optical potential that drives the complete reaction dynamics. In particular, we found that both components critically depend on the angular and radial approach between the reagent partners in determining the collision dynamics.
Evaluation of Electron-Impact Ionization Cross Sections for Molecules
Journal of Physical Chemistry A, 2019
We describe the recent progress in the development of the semi-empirical approach developed by Jain and Khare for the calculations of ionization cross sections for molecules by electron impact. Along with the state-of-the-art description of this approach, the emphasis will be on the evaluation of cross sections for carbon dimer C 2 and trimer C 3 .
The Journal of chemical physics, 2016
The total and ionization cross sections for electron scattering by benzene, halobenzenes, toluene, aniline, and phenol are reported over a wide energy domain. The multi-scattering centre spherical complex optical potential method has been employed to find the total elastic and inelastic cross sections. The total ionization cross section is estimated from total inelastic cross section using the complex scattering potential-ionization contribution method. In the present article, the first theoretical calculations for electron impact total and ionization cross section have been performed for most of the targets having numerous practical applications. A reasonable agreement is obtained compared to existing experimental observations for all the targets reported here, especially for the total cross section.
The Journal of Chemical Physics, 2021
A black box Binary Encounter Bethe (BEB) with an effective core potential (ECP) procedure is implemented, which facilitates the efficient calculation of electron impact ionization cross sections for molecules that include heavy atoms. This is available in the Quantemol electron collisions software, a user friendly graphical user interface to the UKRMol+ codes. Tests were performed for the following series of molecules: CF4, CCl4, CBr4, CI4, and CAt4; CH4, SiH4, GeH4, and SnH4; PH3, PF3, and PCl3; SiCl4 and BCl3; and CH3Br and CF3I. Use of an ECP generally raises the predicted ionization cross section at lower energies leading to improved agreement with experiment compared to all electron calculations for BEB cross sections. Scaling BEB cross sections by the polarizability of the target molecule is shown to give somewhat erratic results, which do not always provide closer agreement with the measured cross sections.