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' 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.
Mono-energetic collision frequency for electrons colliding elastically with various ionospheric t... more Mono-energetic collision frequency for electrons colliding elastically with various ionospheric target gases is averaged over generalized Laguerre functions with appropriate weighting factor. These distribution functions are chosen because they form a complete orthonormal ...
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...
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...
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.
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.
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...
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...
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.
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.
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.
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.
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...
The low-energy e-H{sub 2}S scattering is treated in the static-exchange plus paremeter-free polar... more The low-energy e-H{sub 2}S scattering is treated in the static-exchange plus paremeter-free polarization model. The exchange effects are included exactly by solving the inhomogeneous coupled differential equations iteratively. A recently proposed computationally optimized iterative scheme is employed. The convergence of scattering parameters with respect to the number of iterations is checked for each symmetry and energy. The authors found significant differences between model and the exact exchange results, particularly around the B{sub 2} shape resonance region. They compare their calculations (differential, integral and momentum transfer cross sections) with recent measurements and other calculations employing a local exchange model.
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' 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.
Mono-energetic collision frequency for electrons colliding elastically with various ionospheric t... more Mono-energetic collision frequency for electrons colliding elastically with various ionospheric target gases is averaged over generalized Laguerre functions with appropriate weighting factor. These distribution functions are chosen because they form a complete orthonormal ...
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...
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...
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.
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.
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...
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...
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.
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.
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.
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.
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...
The low-energy e-H{sub 2}S scattering is treated in the static-exchange plus paremeter-free polar... more The low-energy e-H{sub 2}S scattering is treated in the static-exchange plus paremeter-free polarization model. The exchange effects are included exactly by solving the inhomogeneous coupled differential equations iteratively. A recently proposed computationally optimized iterative scheme is employed. The convergence of scattering parameters with respect to the number of iterations is checked for each symmetry and energy. The authors found significant differences between model and the exact exchange results, particularly around the B{sub 2} shape resonance region. They compare their calculations (differential, integral and momentum transfer cross sections) with recent measurements and other calculations employing a local exchange model.
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