Dhanoj Gupta

Electron impact ionization of cycloalkanes, aldehydes, and ketones

The theoretical calculations of electron impact total ionization cross section for cycloalkane, aldehyde, and ketone group molecules are undertaken from ionization threshold to 2 keV. The present calculations are based on the spherical complex optical potential formalism and complex scattering potential ionization contribution method. The results of most of the targets studied compare fairly well with the recent measurements, wherever available and the cross sections for many targets are predicted for the first time. The correlation between the peak of ionization cross sections with number of target electrons and target parameters is also reported. It was found that the cross sections at their maximum depend linearly with the number of target electrons and with other target parameters, confirming the consistency of the values reported here.

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.

Electron impact total ionisation cross sections for simple bio-molecules: a theoretical approach

In this article, we have reported electron impact total ionisation cross sections for the bio-molecules pyridine, pyrimidine, n-propylamine, urea, formamide and N-methylformamide from ionisation threshold to 2000 eV. The present calculations are based on the spherical complex optical potential formalism and complex scattering potential ionisation contribution method. The results obtained for pyridine and pyrimidine are compared with available theoretical and experimental results and are found to be in excellent agreement with existing data. The ionisation cross sections for other molecules are reported for the first time. An interesting relation between the peak of inelastic and ionisation cross sections with target parameters is also reported. It was found that both the cross sections at their maximum depend linearly with these parameters, confirming the consistency of the values reported here.

Elastic and total cross sections for simple biomolecules in the intermediate energy range

The elastic and total cross sections for formaldehyde, acetaldehyde, acetone, 2-butanone and formamide are calculated using the spherical complex optical potential formalism in the intermediate energy range from 50 eV to 10 keV. These cross sections find application to various fields like radiation damage and biological sciences. The present results are compared with the available experimental and theoretical data and are found to give excellent agreement. The elastic cross sections reported for most of the targets in the present energy range are done for the first time. The energy dependence of the contribution of ionization and elastic cross section with respect to the total cross section and the correlation of total cross section with polarizability of the molecules are also studied.

Total ionisation cross sections for chlorofluoromethanes and CClx radicals by electron impact

We report here the total ionisation cross section for chlorofluoromethanes, namely CCl3F (Freon 11), CCl2F2 (Freon 12), CClF3 (Freon 13), CHCl2F (Freon 21), CHClF2 (Freon 22), CH2ClF (Freon 31), CCl4 and CClx (x = 1–3), radicals by electron impact from ionisation threshold to 2 keV. The total inelastic cross section is obtained employing a complex optical potential formalism and solving the Schrödinger equation through partial wave analysis. Using the complex scattering potential-ionisation contribution method, the total ionisation cross section is derived from the inelastic cross section for these targets. The results obtained are then compared with the existing experimental and theoretical data, wherever available. The present result shows reasonable agreement with previous data. For the CClx radicals, the ionisation cross section is predicted for the first time. The data reported here have immense interest to atmospheric and technological plasma modelling.

Electron impact elastic and excitation cross-sections of the isomers of C4F6 molecule for plasma modeling

We report the calculations of elastic (along with its symmetry components) and electronic excitation cross sections by electron impact of the three isomers of C4F6, namely, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6) belonging to the point groups C2, D3d, and C2v, respectively, using the R-matrix approach. The electron energy range is from 0.01 eV to 12 eV. We have employed the cc-pVTZ basis set for C and F atoms to generate self-consistent field molecular orbitals to construct the target states for all the isomers included in our calculations. All the target states are constructed by including correlation effects in a configuration interaction (CI) approach. The target properties such as vertical excitation energies and dipole moment of all the isomers are in reasonable agreement with the literature values. Differences in the cross sections of these isomers are strongly influenced by the effect of correlation and polarization effects and their geometrical extent. We have included the ground state and many excited states of each isomer in the trial wave function of the entire scattering system. The resulting elastic cross sections are compared with the available experimental results. The agreement is reasonably good for energies above 5 eV. The shape resonances detected at 2.57, 2.95, and 3.20 eV for c-C4F6, 1,3-C4F6, and 2-C4F6 isomers are associated with the negative anion formation of C3F3- as observed in the mass spectrometry experiments. We have also performed 1-state CI calculation for all the isomers that include only the correlated ground state. The position of resonances shifts to lower energies as the number of target states is increased compared to 1-state calculation for all the isomers. The elastic cross section for 2-C4F6 isomer is larger than the other isomers because of its larger spatial extent. The present cross section data are important for plasma simulation and modeling, especially related to fluorocarbon plasma.We report the calculations of elastic (along with its symmetry components) and electronic excitation cross sections by electron impact of the three isomers of C4F6, namely, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6) belonging to the point groups C2, D3d, and C2v, respectively, using the R-matrix approach. The electron energy range is from 0.01 eV to 12 eV. We have employed the cc-pVTZ basis set for C and F atoms to generate self-consistent field molecular orbitals to construct the target states for all the isomers included in our calculations. All the target states are constructed by including correlation effects in a configuration interaction (CI) approach. The target properties such as vertical excitation energies and dipole moment of all the isomers are in reasonable agreement with the literature values. Differences in the cross sections of these isomers are strongly influenced by the effect of correlation and polarization effects and their geo...

Electron and positron scattering cross sections for propene

The molecular R-matrix calculation is performed for the low energy electron scattering from propene to obtain total and rotational excitation cross sections. The rotational excitation cross sections are calculated for the transitions involving levels from j = 0 to j = 5. These cross sections are used for calculating their corresponding rate coefficients for the temperature range 30–5000 K. The rate coefficients at such temperatures have relevance in the interstellar medium as well as in the plasma environment. The spherical complex optical potential and complex scattering potential- ionization contribution methods are used for high energy calculation of the total cross section (Qtot) and ionization cross section (Qion), respectively, for both electron and positron scattering. The present Qtot results give reasonable agreement with previous experimental data. We have detected a π * shape resonance for electron scattering at 3.71 eV due to 2A″ scattering state, which is in accordance with the experimental results. However, no such resonance is observed in the positron scattering calculations. The cross sections reported here show good comparison with existing data, validating present calculations and its reliability.The molecular R-matrix calculation is performed for the low energy electron scattering from propene to obtain total and rotational excitation cross sections. The rotational excitation cross sections are calculated for the transitions involving levels from j = 0 to j = 5. These cross sections are used for calculating their corresponding rate coefficients for the temperature range 30–5000 K. The rate coefficients at such temperatures have relevance in the interstellar medium as well as in the plasma environment. The spherical complex optical potential and complex scattering potential- ionization contribution methods are used for high energy calculation of the total cross section (Qtot) and ionization cross section (Qion), respectively, for both electron and positron scattering. The present Qtot results give reasonable agreement with previous experimental data. We have detected a π * shape resonance for electron scattering at 3.71 eV due to 2A″ scattering state, which is in accordance with the experiment...

An R-matrix study of electron induced processes in BF3 plasma

An R-matrix formalism is used to study electron collision with the BF3 molecule using Quantemol-N, a computational system for electron molecule collisions which uses the molecular R-matrix method. Several target models are tested for BF3 in its equilibrium geometry, and the results are presented for the best model. Scattering calculations are then performed to yield resonance parameters, elastic, differential, excitation, and momentum transfer cross sections. The results for all the cross sections are compared with the experimental and theoretical data, and a good agreement is obtained. The resonances have been detected at 3.79 and 13.58 eV, with the ionization threshold being 15.7 eV. We have also estimated the absolute dissociative electron attachment (DEA) cross section for the F− ion production from BF3, which is a maiden attempt. The peak of the DEA is at around 13.5 eV, which is well supported by the resonance detected at 13.58 eV. The cross sections reported here find a variety of applications in t...

Low energy elastic cross section of fluoroacetylene by electron impact

Synopsis Electron impact low energy cross sections for fluoroacetylene is investigated for which there are no reported results in the literature. We have used various target models to compute accurate target properties and the best target model is used for the final scattering calculation. The fluorination effect in the cross section is studied by comparing the results with difluoroacetylene and acetylene.