Kasturi Baluja

Recent Radiative and Collisional Atomic Data of Astrophysical Interest

Le Journal de Physique Colloques, 1988

Electron collisions with the SF2radical using theR-matrix method

Journal of Physics B: Atomic, Molecular and Optical Physics, 2004

ABSTRACT We present the elastic and the excitation cross sections of the four lowest-lying electr... more ABSTRACT We present the elastic and the excitation cross sections of the four lowest-lying electronically excited states of the radical SF2 using the R-matrix method. These excited states have symmetries 1 3A2, 1 1A2, 1 3B1 and 1 1B1. Their vertical excitation energies from the equilibrium geometry of the ground state X 1A1 lie in the range 3.40–6.47 eV. Configuration interaction (CI) wavefunctions are used to represent the target states. In our CI model, we keep the core 14 electrons frozen in doubly occupied molecular orbitals 1a1, 2a1, 3a1, 4a1, 1b1, 1b2 and 2b2. The complete active space consists of 20 valence electrons that are allowed to move freely among the 12 molecular orbitals: 5a1, 6a1, 7a1, 8a1, 9a1, 2b1, 3b1, 3b2, 4b2, 5b2, 6b2 and 1a2. Our calculations do not detect any bound SF−2 states at the equilibrium geometry of the SF2 molecule. We find two shape resonances of 2B2 and 2A1 symmetries with their resonance positions at 1.98 eV and 3.36 eV respectively. Their corresponding resonance widths are 1.52 eV and 2.4 eV. Born correction is applied for the elastic and the dipole allowed transitions to account for higher partial waves excluded in the R-matrix calculation. Total cross sections are presented for incident electron energies up to 15 eV. Calculations with asymmetric stretch of SF2 reveal that 2B2 (2A&#39; in Cs) resonance becomes bound at a bond length beyond 3.9a0. We have also determined the equilibrium geometries, the single bond dissociation energies and the vertical detachment energies of the anionic states. The vertical and adiabatic electron affinity of SF2 are also determined and compared with other works.

Higher order collision frequencies as corrections to Maxwellian distribution function

… Journal of Radio and Space Physics, 1991

Mono-energetic collision frequency for electrons colliding elastically with various ionospheric t... more

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Electron impact cross-sections of tetraethyl silicate

Plasma Sources Science and Technology

Understanding the interactions of electrons with molecules in plasma is of vital importance from ... more Understanding the interactions of electrons with molecules in plasma is of vital importance from both academic and technological points of view. Reliable electron collision data is required to model the electron and ion components of low-temperature and nonequilibrium plasmas. Various electron impact cross sections such as the differential, integral, momentum transfer, partial and total ionizations are reported for tetraethyl silicate (TEOS), a plasma-relevant molecule in the energy range between the ionization threshold and 5 keV. The elastic (differential, integral and momentum transfer) cross sections are obtained by invoking the molecular approach and local potential approximation within the single center expansion formalism. The dissociative ionization cross sections are reported within the binary encounter Bethe (BEB) model formalism. The elastic and ionization cross sections are summed incoherently to estimate total cross sections. A good agreement is observed between the pre...

Electron interactions with AlF

The European Physical Journal D

Partial Ionization Cross Sections of Tungsten Hexafluoride Due to Electron Impact

Atoms

The ionization data of a neutral molecule are crucial to model the energy deposition and dissocia... more The ionization data of a neutral molecule are crucial to model the energy deposition and dissociative ionization process. We study theoretically the electron impact ionization process and report on the dissociative ionization cross sections of the tungsten hexafluoride cations invoking the modified-binary-encounter-Bethe model. In this model, the binary-encounter-Bethe model is modified by applying the transformation to the binding energies of the molecular orbitals and then normalizing the partial ionization cross sections of the cations using the branching ratios. The normalization is performed at a particular energy and ensures that the branching ratios of different fragments are summed to unity. The model yielded satisfactory results for both the singly and doubly ionized ions. The approach validates the results of Basner et al. The advantages and limitations of this model are also discussed. This work corroborates the importance of mass spectrometry data in the proper understan...

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Mass Spectrometry-Based Approach to Compute Electron-Impact Partial Ionization Cross-Sections of Methane, Water and Nitromethane from Threshold to 5 keV

Atoms

The electron impact partial ionization cross-sections of molecules such as methane, water and nit... more The electron impact partial ionization cross-sections of molecules such as methane, water and nitromethane are computed using a modified form of the binary encounter Bethe (BEB) formula. The modified form of the BEB model works on rescaling the molecular binding energies of the orbitals and the scaling of cross-sections using the electron ionization mass spectrometry data. The computed partial ionization cross-sections are consistent with the recommended data and are better than several experimental and theoretical results. The summed partial ionization cross-sections of different fragments also agree with the total ionization cross-sections obtained from BEB and the experimental data. This work highlights the utility of mass spectrometry in the modeling and interpretation of the ionization cross-section data. The limitations and the advantages of the modified form of the BEB model are also discussed.

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The Binary-Encounter-Bethe Model for Computation of Singly Differential Cross Sections Due to Electron-Impact Ionization

Atoms

In the present work, we assess the effectiveness of singly differential cross sections (SDCS) due... more In the present work, we assess the effectiveness of singly differential cross sections (SDCS) due to electron-impact ionization by invoking the binary-encounter-Bethe (BEB) model on various atomic and molecular targets. The computed results were compared with the experimental and theoretical data. A good agreement was observed between the present and the available results. This agreement improves as the incident energy of the projectile increases. The model can be applied to compute the SDCS for the ions produced due to the electron-impact dissociative ionization process and the average energy due to the secondary electrons. Both these quantities are of interest in plasma processing and radiation physics.

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Electron-impact cross sections of acetylene up to 5 keV

The European Physical Journal D

Electron impact cross-sections of tetraethyl silicate

Plasma Sources Science and Technology

Understanding the interactions of electrons with molecules in plasma is of vital importance from ... more Understanding the interactions of electrons with molecules in plasma is of vital importance from both academic and technological points of view. Reliable electron collision data is required to model the electron and ion components of low-temperature and nonequilibrium plasmas. Various electron impact cross sections such as the differential, integral, momentum transfer, partial and total ionizations are reported for tetraethyl silicate (TEOS), a plasma-relevant molecule in the energy range between the ionization threshold and 5 keV. The elastic (differential, integral and momentum transfer) cross sections are obtained by invoking the molecular approach and local potential approximation within the single center expansion formalism. The dissociative ionization cross sections are reported within the binary encounter Bethe (BEB) model formalism. The elastic and ionization cross sections are summed incoherently to estimate total cross sections. A good agreement is observed between the pre...

Electron interactions with AlF

The European Physical Journal D

Partial Ionization Cross Sections of Tungsten Hexafluoride Due to Electron Impact

Atoms

The ionization data of a neutral molecule are crucial to model the energy deposition and dissocia... more The ionization data of a neutral molecule are crucial to model the energy deposition and dissociative ionization process. We study theoretically the electron impact ionization process and report on the dissociative ionization cross sections of the tungsten hexafluoride cations invoking the modified-binary-encounter-Bethe model. In this model, the binary-encounter-Bethe model is modified by applying the transformation to the binding energies of the molecular orbitals and then normalizing the partial ionization cross sections of the cations using the branching ratios. The normalization is performed at a particular energy and ensures that the branching ratios of different fragments are summed to unity. The model yielded satisfactory results for both the singly and doubly ionized ions. The approach validates the results of Basner et al. The advantages and limitations of this model are also discussed. This work corroborates the importance of mass spectrometry data in the proper understan...

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Mass Spectrometry-Based Approach to Compute Electron-Impact Partial Ionization Cross-Sections of Methane, Water and Nitromethane from Threshold to 5 keV

Atoms

The electron impact partial ionization cross-sections of molecules such as methane, water and nit... more The electron impact partial ionization cross-sections of molecules such as methane, water and nitromethane are computed using a modified form of the binary encounter Bethe (BEB) formula. The modified form of the BEB model works on rescaling the molecular binding energies of the orbitals and the scaling of cross-sections using the electron ionization mass spectrometry data. The computed partial ionization cross-sections are consistent with the recommended data and are better than several experimental and theoretical results. The summed partial ionization cross-sections of different fragments also agree with the total ionization cross-sections obtained from BEB and the experimental data. This work highlights the utility of mass spectrometry in the modeling and interpretation of the ionization cross-section data. The limitations and the advantages of the modified form of the BEB model are also discussed.

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The Binary-Encounter-Bethe Model for Computation of Singly Differential Cross Sections Due to Electron-Impact Ionization

Atoms

In the present work, we assess the effectiveness of singly differential cross sections (SDCS) due... more In the present work, we assess the effectiveness of singly differential cross sections (SDCS) due to electron-impact ionization by invoking the binary-encounter-Bethe (BEB) model on various atomic and molecular targets. The computed results were compared with the experimental and theoretical data. A good agreement was observed between the present and the available results. This agreement improves as the incident energy of the projectile increases. The model can be applied to compute the SDCS for the ions produced due to the electron-impact dissociative ionization process and the average energy due to the secondary electrons. Both these quantities are of interest in plasma processing and radiation physics.

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Positron-impact scattering off 1-1 C2H2F2 from 0.1 eV to 4 keV

Physical Review A

Positron-impact cross sections of 1-1-C 2 H 2 F 2 are reported in the energy range from 0.1 to 40... more Positron-impact cross sections of 1-1-C 2 H 2 F 2 are reported in the energy range from 0.1 to 4000 eV. The multicenter Gaussian-type orbitals were expanded within a single determinant Hartree-Fock self-consistent field scheme to obtain molecular wave function. The elastic cross sections were computed within fixed nuclei approximation by invoking the single center expansion approach. The target interactions were described by their local nature. The direct ionization and electron excitation cross sections were estimated using the binaryencounter-Bethe model for positron and scaled-Born approximation, respectively. The experimental scattering data were corrected to account for the angular discrimination effects. The corrections enhanced experimental measurements substantially in the low-energy range. The elastic cross sections are in an excellent agreement with the forward angle corrected total cross sections below positronium formation. The cross sections obtained by summing the elastic and inelastic cross sections incoherently were in good agreement with the experimental results. An in-depth analysis of the angular limitation of spectrometers employed in measuring the positron impact scattering cross sections and corrections arising out of the polar molecule are an integral part of the study. Some key aspects of electron and positron scattering are also discussed.

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Electron-impact cross sections of acetylene up to 5 keV

The European Physical Journal D

Positron-impact scattering off 1-1 C2H2F2 from 0.1 eV to 4 keV

Physical Review A

Positron-impact cross sections of 1-1-C 2 H 2 F 2 are reported in the energy range from 0.1 to 40... more Positron-impact cross sections of 1-1-C 2 H 2 F 2 are reported in the energy range from 0.1 to 4000 eV. The multicenter Gaussian-type orbitals were expanded within a single determinant Hartree-Fock self-consistent field scheme to obtain molecular wave function. The elastic cross sections were computed within fixed nuclei approximation by invoking the single center expansion approach. The target interactions were described by their local nature. The direct ionization and electron excitation cross sections were estimated using the binaryencounter-Bethe model for positron and scaled-Born approximation, respectively. The experimental scattering data were corrected to account for the angular discrimination effects. The corrections enhanced experimental measurements substantially in the low-energy range. The elastic cross sections are in an excellent agreement with the forward angle corrected total cross sections below positronium formation. The cross sections obtained by summing the elastic and inelastic cross sections incoherently were in good agreement with the experimental results. An in-depth analysis of the angular limitation of spectrometers employed in measuring the positron impact scattering cross sections and corrections arising out of the polar molecule are an integral part of the study. Some key aspects of electron and positron scattering are also discussed.

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Global Analysis of Long-Term Trends in Total Ozone Derived from Dobson or Ground Based Instrument Data

MAUSAM, 2021

1. The abundance of atmospheric ozone is determined by a combination of chemical and dynamical pr... more 1. The abundance of atmospheric ozone is determined by a combination of chemical and dynamical processes. The importance of these processes changes with time and location. These processes also act on different time scales, e.g., solar cycle varies over 11 years and strong volcanic eruptions have an effect lasting a few years only. The study of long-term trend of ozone in the different regions of the globe is at the forefront of research in the atmospheric chemistry.

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Global Analysis of Long-Term Trends in Total Ozone Derived from Dobson or Ground Based Instrument Data

MAUSAM, 2021

1. The abundance of atmospheric ozone is determined by a combination of chemical and dynamical pr... more 1. The abundance of atmospheric ozone is determined by a combination of chemical and dynamical processes. The importance of these processes changes with time and location. These processes also act on different time scales, e.g., solar cycle varies over 11 years and strong volcanic eruptions have an effect lasting a few years only. The study of long-term trend of ozone in the different regions of the globe is at the forefront of research in the atmospheric chemistry.

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Elastic and Inelastic Cross Sections for Low-Energy Electron Collisions with ClF Molecule Using the R-Matrix Method

Atoms, 2022

The ClF molecule belongs to an interhalogen family and is important in laser physics and condense... more The ClF molecule belongs to an interhalogen family and is important in laser physics and condensed phase molecular dynamics. The elastic and excitation scattering cross sections are obtained in a fixed nuclei approximation using the UKRmol+ codes based on R-matrix formalism. The scattering calculations were performed in the static-exchange (SE), static-exchange-plus-polarisation (SEP), and close-coupling (CC) models. Three CC models with different target states were employed, namely, the 1-state, 5-states, and 12-states. In the CC model, the target states were represented by configuration interaction (CI) wavefunctions. A good agreement of dipole and quadrupole moments of the ground state was obtained with the experimental values, which indicates a good representation of the target modelling. The study predicted the existence of a shape resonance in the SE, SEP, and 5-states CC models. This resonance vanished in the 12-states CC model. The excitation cross sections from ground to th...

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