Spherical Complex Optical Potential Research Articles

Calculation of electron-impact ionization of various benzene derivatives

Calculations of the electron-impact ionization cross-section of pyrene, anthracene, benzoyl chloride, benzophenone, and phthalonitrile are reported over a wide energy range. A comparison of theoretical models, viz. spherical complex optical potential (SCOP), pixel counting method (PCM), and the binary encounter Bethe (BEB) model is carried out. SCOP calculations provide the inelastic cross-section, and the ionization cross-section is extracted from it. This result is modified with PCM, a model previously applied to ion collisions which takes geometric screening corrections into account. The BEB model is used as an independent approach to calculate the ionization cross-section. It is demonstrated that all model results are in reasonable agreement with each other. Comparison is also made with other theoretical data where available.

Electron interactions with beryllium and its hydrides

In present study of electron driven inelastic processes, we report calculated probabilities of inelastic events (including total inelastic and ionizations) occurrence by quantifying the cross sections, Qinel and Qion for beryllium (Be) and beryllium hydrides viz. BeH, BeH2, Be2H2 and Be2H4 from the molecular ionization threshold to 5 keV. The Spherical Complex Optical Potential (SCOP) to compute Qinel has been employed and Qion is extracted using Complex Scattering Potential –ionization contribution (CSP-ic) approximation. Owing to the toxic character of beryllium compounds we do not find any experimental work for these molecules. In paucity of the experimental data, present work is important and will fill the void of the data needed for particular in plasma physics, aero science, astrophysics and chemical analysis. This study is the maiden report of Qinel for all of these important targets.

Molecular processes for radiosensitizer compounds upon electron interactions

This work presents a theoretical analysis of electron impact elastic and inelastic processes for oxygen mimic and fluorinated radiosensitizer molecules over a wide energy range, spanning from ionization potential (IP) to 5 keV. The computation to determine elastic (Qel), inelastic cross sections (Qinel) and total cross sections (QT) is done through the Spherical Complex Optical Potential (SCOP) formalism and ionization cross sections (Qion) and summed excitation cross sections (∑Qexc) are deduced through the Complex Scattering Potential ionization contribution (CSP-ic) formalism. Additionally, a recently developed an alternative approach for complex and large molecules (55≤Z≤95), namely the Two Parameters Semiempirical Method (2p-SEM), for impact energy 50 eV to 5 keV is employed to estimate Qel and QT. These radiosensitizer molecules, imidazole, 2-nitroimidazole, 2-nitrofuran, 4(5)-nitroimidazole, pentafluorobenzoic acid, perfluorothiophenol are of particular interest due to their applications in cancer therapy treatment. Cross sections allow us to assess the probability of various molecular Processes occurring due to electron interaction. This work is the first report of the estimation of this electron driven molecular processes for these radiosensitizers except for imidazole and 2-Nitroimidazole where previous Qion results are available. Our Present results are in good accordance with available data from existing literature. The study incorporates various correlations to show size dependency of various cross sections and linear correlation of Qion vs. impact energy, Qel vs. impact energy, QT vs. impact energy and linear correlation of Qion (Max) vs. αI to confirm the credibility and consistency of the present results.

Theoretical investigation of electron interaction processes for furfural (C5H4O2) and p-benzoquinone (C6H4O2)

The present study aims to quantify the electron-induced inelastic and elastic processes for molecules of industrial relevance, furfural and p-benzoquinone. We have computed inelastic cross-sections (Qinel), elastic cross-sections (Qel) and total cross-sections (QT) through spherical complex optical potential (SCOP) formalism, from ionisation energy (IE) to 5000 eV. The continuum and discrete contributions of the Qinel have been calculated in terms of ionisation (Qion) and excitation (∑Qexc) cross-sections, respectively, by employing the complex scattering potential-ionisation contribution (CSP-iC) method. A novel 2-parameter semi-empirical method (2p-SEM), a useful approach applicable for the large molecules 55 < Z < 95 for calculating QT, has been proposed and validated. Computed results are compared with previous experimental and theoretical data. We have also estimated the dielectric constant (ε) using various methods and correlations with molecular ionisation for these applied molecules.

Electron-driven molecular processes for cyanopolyacetylenes HC2n+1N (n = 3, 4, and 5).

Linear carbon series cyanopolyacetylenes (HC2n+1N) (n = 3, 4, and 5) are astromolecules found in the atmosphere of Titan and interstellar media such as TMC-1 (Taurus molecular cloud-1). All these compounds are also detected in IRC + 10 216. In the present work, we comprehensively investigate electron interaction with important cyanopolyacetylene compounds, viz. HC7N (cyano-tri-acetylene), HC9N (cyano-tetra-acetylene), and HC11N (cyano-penta-acetylene). The study covers incident electron energies ranging from the ionization threshold to 5 keV. Various electron-driven molecular processes are quantified in terms of total cross-sections. The quantum spherical complex optical potential (SCOP) is used to determine elastic (Qel) and inelastic (Qinel) cross-sections. Ionization is the most important inelastic effect that opens various chemical pathways for the generation of different molecular species; we computed the ionization cross-section (Qion) and discrete electronic excitation cross-section (ΣQexc) using the complex scattering potential-ionization contribution (CSP-ic) method. The cyanopolyacetylene compounds are difficult to handle experimentally owing to the health risks involved. Therefore, there are no prior experimental data available for these molecules; only Qion have been reported theoretically. Thus, the present work is the maiden report on computing Qel, Qinel, ΣQexc, and QT. In order to provide an alternative approach and further validation of the present work, we employed our recently developed two-parameter semi-empirical method (2p-SEM) to compute Qel and QT. Additionally, we predict the polarizability of the HC11N molecule, which has not been reported in the existing literature. This prediction is based on a correlation study of polarizabilities of molecules with Qion values from the same series of molecules.

Electron- and positron-driven molecular processes for H2O, CO2, and NH3 in their gas and ice phases.

In this comprehensive study, we explored the molecular chemistry of H2O, CO2, and NH3 molecules in their gas and ice phases assisted by electron and positron interactions over a wide range of energy from threshold to 5000 eV. These simple molecules have immense applications in areas such as atmospheric sciences and astrochemistry. We employed the spherical complex optical potential (SCOP) model along with the complex scattering potential-ionization contribution (CSP-ic) model and modified them to quantify the probabilities of various charged particle-driven molecular processes through inelastic cross-sections (Qinel), total ionization cross-sections (Qion), direct ionization cross-sections (QD-ion), and positronium formation cross-sections (QPs) for these molecules in gas and ice phases. We propose a novel model that incorporates the band gap of a material for positron impact cross-sections with molecules in their condensed phase. This is the first study on electron interactions with NH3 (ice) and positron interactions with H2O, CO2, and NH3 in their condensed phase.

Electron interactions with analogous of DNA/RNA nucleobases: 3-hydroxytetrahydroFuran and α-Tetrahydrofurfuryl alcohol

We report quantitative results for electron induced molecular processes for DNA/RNA nucleobase analogous bio-molecules, 3-hydroxytetrahydrofuran (C4H8O2, 3hTHF) and α-tetrahydrofurfuryl alcohol (C5H10O2, THFA), which are similar in structure and functional group to backbone of DNA and RNA. We have employed spherical complex optical potential (SCOP) formalism to compute total elastic (Qel) and inelastic (Qinel) cross sections and used Complex Scattering Potential-ionization contribution (CSP-ic) method to obtain total ionization (Qion) and summed total excitation (∑Qexc) cross sections. These results obtained for a wide energy range (10 eV - 5 keV) may serve as the input parameters in predicting damage in biomolecular systems induced by secondary electrons caused by primary ionization radiation. We have observed a correlation between maximum Qion and molecular polarizability volume (α), ionisation energy (IE) and number of valence electrons (Nv). This work includes an attempt to estimate ∑Qexc for these molecules in normal state.

Electron impact inelastic molecular processes for deuterated compounds

In this theoretical work, electron induced inelastic molecular processes for deuterated molecules HD, D2, D2O, SiDx (x = 1–3), NDx (x = 1–3) and CDx (x = 2–4) are studied and quantified from ionisation threshold to 5 keV. The total inelastic cross section (Qinel) are computed using Spherical Complex Optical Potential (SCOP) and total ionisation cross sections (Qion) and total electronic excitation cross sections (∑Qexc) have been evaluated through the Complex Spherical Potential – ionisation contribution (CSP-ic) method. Electron driven inelastic effects for deuterated hydrogen (HD) are investigated for the first time in this study. This is the first report of total Qion for HD, SiDx (x = 1–3), NDx (x = 1,2), CDx (x = 2,3) molecules and maiden study of Qinel and ∑Qexc for all these molecules. Further, isotope effect is studied for these targets and using various correlation analyses, dipole polarizability for ND and SiDx (x = 1–3) molecules are predicted.

Dynamics of electron collision with potential biofuel: N-butanol

A detailed theoretical investigation of electron impact collision on n-butanol, a potential biofuel, is carried out over a wide energy impact range from 0.1 to 5000 eV. The low energy scattering calculations from 0.1 to 20 eV are performed using UK molecular R-matrix method via Quantemol-N software. This scattering investigation aims to predict various resonances by providing dissociative electron attachment via C–O bond cleavage. Furthermore, the study focuses on estimating several cross-sections namely elastic, differential, momentum transfer, excitation, ionization and total cross-section. In addition, we also computed higher energy cross-section from the ionization threshold to 5000 eV using the spherical complex optical potential (SCOP) method. A good agreement is observed between the computed cross-section at the overlapping energies of employing (SCOP and R-matrix) formalisms. Apart from the scattering study, we also obtained various resonances having significance at low energy. Theoretically predicted resonance peaks agree well with previously reported data and a few new resonance states are also identified. The cross-sectional data presented here will be beneficial as an input parameter modelling electron transport processes during the spark ignition.

Electron impact ionisation and other molecular processes for organoplatinum compounds

Electron interactions with platinum-based chemotherapeutic organoplatinum compounds, cisplatin (H6N2Cl2Pt), nedaplatin (C2H8N2O3Pt), carboplatin (C6H12N2O4Pt) and oxaliplatin (C8H14N2O4Pt), are studied for ionisation and other molecular processes from ionisation potential (IP) to 5 keV. Elastic cross sections Q el, inelastic cross sections Q inel and total cross sections Q T are computed using Spherical Complex Optical Potential (SCOP) formalism and ionisation cross-sections Q ion and summed excitation cross sections ∑Q exc are derived through Complex Scattering Potential – ionisation contribution (CSP-ic) method. Only theoretical data is available in the literature for these molecules and we find good accord with them. This is the first report of Q T, Q inel and Q exc for all these molecules and Q el for Nedaplatin.

Electron scattering from molecules relevant to Titan's atmosphere

Present article reports calculation of elastic, momentum transfer, ionization, and total cross sections for electron scattering from C2N2, C4N2, C6N2, and HC5N molecules, relevant to Titan's atmosphere. The cross sections are predicted using spherical complex optical potential and complex potential ionization contribution method in the energy range from ionization threshold of the molecules to 5 keV. The cross section data reported here consider geometrical screening correction to avoid overestimation of cross section due to the overlap of charge density. A strong correlation is observed between Qionmax and (α/I)12 for C2N2, C4N2, and C6N2 molecular systems, which confirms the consistency of predicted ionization data. The cross sections reported here are important for mass spectrometry, especially in modelling Titan's atmosphere due the presence of these molecules along with abundant electrons in its environment. Most of the data are reported for the first time.

Theoretical investigation of electron impact on formyl fluoride (HFCO)

In this paper, a descriptive and detailed theoretical analysis is carried out on electron scattering of formyl fluoride (HFCO) covering a wide impact energy range of 0.1 eV–5000 eV. Due to such a wide impact energy range, we were able to calculate the variety of interaction processes such as eigen phase study to infer about the resonances, vertical electron excitations, differential cross-sections, momentum transfer cross-sections, ionization cross-sections and total scattering cross-sections for electron impact on formyl fluoride. To compute these cross-sections for this energy range, we have used an amalgamation of two theoretical methodologies namely R-matrix via. Quantemol-N, valid for the low energy calculations from 0.1 eV to 20 eV and the Spherical Complex Optical Potential (SCOP) applicable from ionization threshold of the target to 5000 eV. There is a smooth cross over of total cross-sections observed between these two methods at the incident energy just below 20 eV. The present study becomes more important as it presents the electron impact cross-sections on HFCO for the first time and thus provides a reference data set for HFCO over an extensive impact energy range. The data set is important as Hydrofluorocarbons (HFCs) are one class of potential chlorofluorocarbons (CFC) substituents which mainly reacts with the OH radical in the atmosphere leading to the formation of the dominant intermediate product HFCO.

Positron Scattering from Atoms and Molecules

A review on the positron scattering from atoms and molecules is presented in this article. The focus on positron scattering studies is on the rise due to their presence in various fields and application of cross section data in such environments. Positron scattering is usually investigated using theoretical approaches that are similar to those for electron scattering, being its anti-particle. However, most experimental or theoretical studies are limited to the investigation of electron and positron scattering from inert gases, single electron systems and simple or symmetric molecules. Optical potential and polarized orbital approaches are the widely used methods for investigating positron scattering from atoms. Close coupling approach has also been used for scattering from atoms, but for lighter targets with low energy projectiles. The theoretical approaches have been quite successful in predicting cross sections and agree reasonably well with experimental measurements. The comparison is generally good for electrons for both elastic and inelastic scatterings cross sections, while spin polarization has been critical due to its sensitive perturbing interaction. Positron scattering cross sections show relatively less features than that of electron scattering. The features of positron impact elastic scattering have been consistent with experiment, while total cross section requires significant improvement. For scattering from molecules, utilization of both spherical complex optical potential and R-matrix methods have proved to be efficient in predicting cross sections in their respective energy ranges. The results obtained shows reasonable comparison with most of the existing data, wherever available. In the present article we illustrate these findings with a list of comprehensive references to data sources, albeit not exhaustive.

Calculation of electron scattering cross sections for Anthracene, Pyridine and Warfarin molecules over energy range 10–30000 eV

This paper reports electron impact total cross section, total elastic, total inelastic and differential cross sections for molecules Anthracene, Pyridine and Warfarin having been computed using the independent atom model with screening-corrected additivity rule over an incident energy range of 10–30000 eV. The calculations are performed with relativistic (Dirac) partial-wave for scattering by applying a local central interaction potential V(r). A model spherical complex optical potential is used for calculations. Good agreement is achieved in intermediate and high-energy zones.

Electron interactions with astro chemical compounds

In present work electron induced processes with important astro-compounds found in the tholins of Titan are investigated. We report calculated total elastic cross sections Qel, total inelastic cross sections Qinel, total ionization cross sections Qion, total excitation cross sections ∑Qexc and total cross sections QT for hydrogen cyanide (HCN), cyanoacetylene (HCCCN), vinyl cyanide (CH2CHCN), methanimine (CH2NH) and ethanimine (CH3CHNH) on electron impact for energies from ionization threshold to 5 keV. We have employed the Spherical Complex Optical Potential (SCOP) formalism to investigate elastic as well as inelastic processes and used Complex Scattering Potential – ionization contribution (CSP-ic) method to derive ionization cross sections. In absence of any theoretical or experimental data of ionization cross sections except for HCN and HCCCN, we have computed Qion using the Binary- Encounter- Bethe (BEB) method for all these molecules and have found reasonable agreement. This is the maiden attempt to report various total cross sections for all these astro-molecules except HCN and HCCCN.

Inelastic cross sections for pentane isomers by positron impact

ABSTRACTThis work aims at the calculation of various inelastic cross sections for three pentane isomers, namely normal pentane, isopentane and neopentane. The direct ionisation, positronium formation, total ionisation and total inelastic cross section are reported for these targets using modified spherical complex optical potential (mSCOP) and complex scattering potential-ionisation contribution (CSP-ic) method. The cross sections are computed for a wide energy range from their respective thresholds to 5 keV. We have also attempted to probe the isomeric effect in the inelastic scattering of positrons from the pentane isomers. The cross sections for the three isomers were found to overlap for the entire comparative energy range except at the peak region. Hence, in general no appreciable isomeric effect was beheld for the pentane isomers.

Ionization of P Atom, P\(_2\) and PX (X = H, C, N, O) Molecules by Electron Impact: Theoretical Studies

Being a biogenic element atomic Phosphorus is one of the significant constituents of the universe [1]. Gulick [2] found a pivotal role of phosphorus in the origin of life. The phosphoruscontaining molecules like PH, PC and PN radicals, have been observed in interstellar gas clouds [3–5] and they are proposed to be present under appropriate conditions. Phosphorous hydrides having numerous applications, are detected in cool stellar atmosphere [6] and circumstellar envelopes. Thus, the present paper addresses the electron impact processes of atomic phosphorus and its diatomic compounds. Ground and metastable states of Atomic P give rise to the probability of presence of metastable state in the atomic beam used for cross section measurement [7]. We have employed the well-known Spherical Complex Optical Potential (SCOP) formalism to calculate total inelastic cross sections. The semi-empirical CSP- ic method is used to extract total ionization cross section \(Q_{ion}\) from total inelastic cross section [8]. A variant CSP- ic approach is also attempted for these targets.

Electron impact scattering study on chlorobenzene

ABSTRACTIn this article, we report a detailed theoretical study on electron interactions with chlorobenzene with incident energies ranging from 0.1 to 5000 eV. Due to this wide range of impact energy, we are able to investigate a variety of processes and report data on resonances, differential cross-sections (DCS), momentum transfer cross-sections (MTCS), rate coefficient, vertical electronic excitations, dissociative electron attachment (DEA), total ionisation cross-sections and total scattering cross-sections (TCS). In order to compute the total scattering cross-sections, we have employed the ab-initio R-matrix method via Quantemol-N for the lower energy range (0.1 eV to 20 eV) and Spherical Complex Optical Potential (SCOP) beyond threshold energy of the target to 5000 eV. The R-matrix calculations are performed using a close-coupling method with the aid of 34 target states, 1667 configuration state functions, and 233 channels employing Configuration Interaction (CI) model. The present study reports evidence for electron scattering resonances through analysis of eigenphase diagrams fitting them to Breit-Wigner profile at low energies below the ionisation threshold.

Computation of electron impact scattering studies on benzene

An elaborate theoretical study of electron scattering with benzene over a broad impact energy range is reported in this article. Integrated cross sections such as the electronic excitation cross section, momentum transfer cross section, ionization cross section and the total collision cross section along with the differential elastic cross section are computed at low energy (0.01–20 eV) using ab initio R-matrix employing Quantemol-N. Beyond ionization threshold, the calculations are also carried out using spherical complex optical potential (SCOP) formalism up to 5000 eV. A smooth crossover of the total cross section data is obtained through the two formalisms at the incident energy equal to 13 eV and hence we are able to study the cross sections over a wide energy range. The scattering rate coefficients using the computed elastic cross sections for this target are reported for the first time.

Theoretical study of positron scattering from pentane isomers

This work aims to probe isomeric effect in case of positron scattering. In this pursuit, we have chosen pentane (C5H12) as the target molecule. The structural isomers of pentane offers a perfect prototype to investigate isomeric effect and thus may give further knowledge into the role of the geometrical arrangements of atoms in a target molecule during the positron scattering process. The grand total, integral elastic and differential cross section are reported using the modified spherical complex optical potential (mSCOP) method. The cross sections do not exhibit isomeric effect, which is in accordance with the experimental observation.