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V. Laporta

Publications and source records attributed to V. Laporta.

At least 19 recordsLinked to original sources
arXiv2026

Electron-impact cross sections for dissociation processes of vibrationally excited CH radical

This paper presents a theoretical investigation of the cross sections for dissociative electron attachment and dissociative excitation processes in vibrationally excited CH radicals induced by electron impact. Resonant electron-CH collisions are analyzed using the ab-initio R-matrix method, while nuclear dynamics are explored within the Local Complex Potential framework. A comprehensive set of vibrationally resolved cross sections and rate coefficients is provided for both the ground and first excited electronic states of the CH molecule. These findings contribute to a better understanding of the kinetics of non-equilibrium systems containing CH molecules with applications in plasma technologies for CO2 reduction, combustion processes and various astrophysical contexts.

physics.atom-ph↗
arXiv2024

Low-energy collisions between electrons and BeD$^+$

Multichannel quantum defect theory is applied in the treatment of the dissociative recombination and vibrational excitation processes for the BeD$^+$ ion in the twenty four vibrational levels of its ground electronic state ($\textrm{X}\,{^{1}\Sigma^{+}},v_{i}^{+}=0\ldots 23$). Three electronic symmetries of BeD$^{**}$ states (\ensuremath{^{2}\Pi}, \ensuremath{^{2}\Sigma^{+}}, and \ensuremath{^{2}\Delta}), are considered in the calculation of cross sections and the corresponding rate coefficients. The incident electron energy range is $10^{-5}$--2.7 eV and the electron temperature range is 100--5000~K. The vibrational dependence of these collisional processes is highlighted. The resulting data are useful in magnetic confinement fusion edge plasma modelling and spectroscopy, in devices with beryllium based main chamber materials, such as ITER and JET, and operating with the deuterium-tritium fuel mix. An extensive rate coefficients database is presented in graphical form and also by analytic fit functions whose parameters are tabulated in the supplementary material.

physics.plasm-ph↗
arXiv2023

Reactive collisions between electrons and BeH+ above dissociation threshold

Our previous studies of dissociative recombination, and vibrational excitation/de-excitation of the BeH$^+$ ion, based on the multichannel quantum defect theory, are extended to collision energies above the dissociation threshold, taking into account the vibrational continua of the BeH$^+$ ion and, consequently, its dissociative excitation. We have also significantly increased the number of dissociative states of $^2{\Pi}$, $^2{\Sigma}^+$ and $^2\Delta$ symmetry included in our cross section calculations, generating the most excited-ones by using appropriate scaling laws. Our results are suitable for modeling the kinetics of BeH+ in edge fusion plasmas for collision energies up to 12 eV.

physics.atom-ph↗
arXiv2022

Reactive collisions between electrons and BeT$^+$: Complete set of thermal rate coefficients up to 5000 K

Rate coefficients for the dissociative recombination, vibrational excitation and vibrational de-excitation of the BeT$^{+}$ ion for all vibrational levels of its ground electronic state ($ X\ensuremath{^{1}Σ^{+}},v_{i}^{+}=0,\dots,27$) are reported, including in the calculation the contribution of super-excited states of the BeT complex pertaining to three electronic symmetries - $^{2}Π$, $^{2}Σ^{+}$, and $^{2}Δ$. These data are suitable for the kinetic modeling of beryllium and tritium containing plasma, as encountered in magnetic fusion devices with beryllium walls (JET, ITER). In the present study we restrict ourselves to incident electron energies from 10$^{-3}$ up to $2.7$ eV, and to electron temperatures between $100$ and $5000$ K, respectively. Together with our earlier and closely related studies on the BeH$^{+}$ and BeD$^{+}$ systems, this present work completes the isotopic coverage for the beryllium monohydride ions. The vibrational energy (rather than the vibrational quantum state) is identified as a proper isotopic similarity parameter, e.g., for reduced but still isotopically correct plasma chemistry models.

physics.atom-ph↗
arXiv2022

Electron driven reactive processes involving H$^+_2$ and HD$^+$ molecular cations in the Early Universe

We describe the major low-energy electron-impact processes involving H$^+_2$ and HD$^+$, relevant for the astrochemistry of the early Universe: Dissociative recombination, elastic, inelastic and superelastic scattering. We report cross sections and Maxwellian rate coefficients of both rotational and vibrational transitions, and outline several important features, like isotopic, rotational and resonant effects.

astro-ph.IM↗
arXiv2020

Dissociative electron attachment cross sections for ro-vibrationally excited NO molecule and N- anion formation

Motivated by the huge need of data for non-equilibrium plasma modeling, a theoretical investigation of dissociative electron attachment to the NO molecule is performed. The calculations presented here are based on the Local-Complex-Potential approach, taking into account five NO$^-$ resonances. Three specific channels of the process are studied, including the production of excited nitrogen atoms $\mathrm{N}(^2\mathrm{D})$ and of its anions N$^-$. Interpretation of the existing experimental data and their comparison with our theoretical result are given. A full set of ro-vibrationally-resolved cross sections and the corresponding rate coefficients are reported. In particular, a relatively notably large cross section of N$^-$ ion formation at low energy of the incident electron and for vibrationally excited NO target is predicted. Finally, molecular rotation effects are discussed.

physics.atom-ph↗
arXiv2020

Vibrationally resolved NO dissociative excitation cross sections by electron impact

A theoretical investigation of the dissociative excitation by electron impact on the NO molecule is presented, aiming to make up for the lack of data for this process in the literature. A full set of vibrationally-resolved cross sections and corresponding rate coefficients are calculated using the Local-Complex-Potential approach and five resonant states of NO^-.

physics.atom-ph↗
arXiv2018

Theoretical study of ArH+ dissociative recombination and electron-impact vibrational excitation

Cross sections are presented for dissociative recombination and electron-impact vibrational excitation of the ArH+ molecular ion at electron energies appropriate for the interstellar environment. The R-matrix method is employed to determine the molecular structure data, i.e. the position and width of the resonance states. The cross sections and the corresponding Maxwellian rate coefficients are computed using a method based on the Multichannel Quantum Defect Theory. The main result of the paper is the very low dissociative recombination rate found at temperatures below 1000K. This is in agreement with the previous upper limit measurement in merged beams and offers a realistic explanation to the presence of ArH+ in exotic interstellar conditions.

astro-ph.GA↗
arXiv2018

Reactive collision of electrons with CO$^+$ in cometary coma

In order to improve our understanding of the kinetics of the cometary coma, theoretical studies of the major reactive collisions in these environments are needed. Deep in the collisional coma, inelastic collisions between thermal electrons and molecular ions result in recombination and vibrational excitation, the rates of these processes being particularly elevated due to the high charged particle densities in the inner region. This work addresses the dissociative recombination, vibrational excitation, and vibrational de-excitation of electrons with CO$^+$ molecular cations. The aim of this study is to understand the importance of these reactive collisions in producing carbon and oxygen atoms in cometary activity. The cross-section calculations were based on Multichannel Quantum Defect Theory. The molecular data sets, used here to take into account the nuclear dynamics, were based on ab initio R-matrix approach. The cross sections for the dissociative recombination, vibrational excitation, and vibrational de-excitation processes, for the six lowest vibrational levels of CO$^+$ - relevant for the electronic temperatures observed in comets - are computed, as well as their corresponding Maxwell rate coefficients. Moreover, final state distributions for different dissociation pathways are presented. Among all reactive collisions taking place between low-energy electrons and CO$^+$, the dissociative recombination is the most important process at electronic temperatures characterizing the comets. We have shown that this process can be a major source of O($^3$P), O($^1$D), O($^1$S), C($^3$P) and C($^1$D) produced in the cometary coma at small cometocentric distances.

astro-ph.EP↗
arXiv2016

Calculated low-energy electron-impact vibrational excitation cross sections for CO2 molecule

Vibrational-excitation cross sections of ground electronic state of carbon dioxide molecule by electron-impact through the CO2-(2Π) shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume decoupling between normal modes and employ the local complex potential model for the treatment of the nuclear dynamics, usually adopted for the electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and comparison with data present in the literature is discussed.

physics.chem-ph↗
arXiv2015

Electron-impact dissociation cross sections of vibrationally excited He2+ molecular ion

Electron-impact cross sections for the dissociation process of vibrationally excited He2+ molecular ion, as a function of the incident electron energy are calculated for the dissociative transition X2Σ+u \to A2Σ+g by using the R-matrix method in the adiabatic-nuclei approximation. The potential energy curves for the involved electronic states and target properties, also calculated with the R-matrix method, were found to be in good agreement with the results reported in literature.

physics.plasm-ph↗
arXiv2015

Dissociative electron attachment and electron-impact resonant dissociation of vibrationally excited O2 molecules

State-by-state cross sections for dissociative electron attachment and electron-impact dissociation for molecular oxygen are computed using ab initio resonance curves calculated with the R-matrix method. When O2 is in its vibrational ground state, the main contribution for both processes comes from the $^2Π_u$ resonance state of $O_2^-$ but with a significant contribution from the $^4Σ$ resonant state. Vibrational excitation leads to an increased contribution from the low-lying $^2Π_{g}$ resonance, greatly increased cross sections for both processes, and the threshold moving to lower energies. These results provide important input for models of O2-containing plasmas in nonequilibrium conditions.

physics.plasm-ph↗
arXiv2014

Electron-impact resonant vibrational excitation and dissociation processes involving vibrationally excited N2 molecules

Resonant vibrational excitation cross sections and the corresponding rate coefficients for electron-N$_2$ collisions occurring through the N$_2^-(\textrm{X}\ ^2Π_g)$ resonant state are reviewed. New calculations are performed using accurate potential energies curves for the N$_2$ electronic ground state, taken from literature, and for the N$_2^-$ resonant state, obtained from $R$-matrix calculations. The calculations are extended also to the resonant excitation processes involving the N$_2$ ground state vibrational continuum, leading to dissociation. Electron impact dissociation is found to be significant from higher vibrational levels. Accurate analytical fits for the complete set of the rate coefficients are provided. The behavior of the dissociative cross sections is investigated for rotationally excited N$_2$ molecules, with $J=50,100$ and 150 and for different vibrational levels.

physics.plasm-ph↗
arXiv2013

Electron-vibration energy exchange models in nitrogen-containing plasma flows

The physics of vibrational kinetics in nitrogen-containing plasma produced by collisions with electrons is studied on the basis of recently derived cross sections and rate coefficients for the resonant vibrational-excitation by electron-impact. The temporal relaxation of the vibrational energy and of the vibrational distribution function is analyzed in a state-to-state approach. The electron and vibrational temperature are varied in the range of [0,50000] K. Conclusions are drawn with respect to the derivation of reduced models and to the accuracy of a relaxation time formalism. A analytical fit of the vibrational relaxation time is given.

physics.chem-ph↗
arXiv2012

Theoretical vibrational-excitation cross sections and rate coefficients for electron-impact resonant collisions involving rovibrationally excited N2 and NO molecules

Electron-impact vi->vf vibrational excitations cross sections, involving rovibrationally excited N_{2}(v_{i}, J) and NO(v_{i}, J) molecules (fixed J), are calculated for collisions occurring through the nitrogen resonant electronic state N_{2}^{-} (X ^{2}Π_{g}), and the three resonant states of nitric oxide NO^{-}(^{3}Σ^{-},^{1} Δ,^{1} Σ^{+}). Complete sets of cross sections have been obtained for all possible transitions involving 68 vibrational levels of N2(X ^{1}Σ^{+}_{g}) and 55 levels of NO(X ^{2}Π), for the incident electron energy between 0.1 and 10 eV. In order to study the rotational motion in the resonant processes, cross sections have been also computed for rotationally elastic transitions characterized by the rotational quantum number J running from 0 through 150. The calculations are performed within the framework of the local complex potential model, by using potentials energies and widths optimized in order to reproduce the experimental cross sections available in literature. Rate coefficients are calculated for all the (v_{i}, J) \rightarrow (v_{f}, J) transitions by assuming a Maxwellian electron energy distribution function in the temperature range from 0.1 eV to 100 eV. All the produced numerical data can be accessed at http://users.ba.cnr.it/imip/cscpal38/phys4entry/database.html.

physics.plasm-ph↗
arXiv2012

Electron--impact resonant vibration excitation cross sections and rate coefficients for carbon monoxide

Resonant vibrational and rotation-vibration excitation cross sections for electron-CO scattering are calculated in the 0-10 eV energy range for all 81 vibrational states of CO, assuming that the excitation occur via the 2Π shape resonance. Static exchange plus polarization calculations performed using the R-matrix method are used to estimate resonance positions and widths as functions of internuclear separation. The effects of nuclear motion are considered using a local complex potential model. Good agreement is obtained with available experimental data on excitation from the vibrational ground state. Excitation rates and cross sections are provided as a functions of the initial CO vibrational state for all ground state vibrational levels.

physics.chem-ph↗
arXiv2007

Non leptonic B decays to axial-vector mesons and factorization

We present an analysis of two-body B decays with a pseudoscalar (P) and an axial-vector meson (A) in the final state using naive factorization. We employ as inputs a limited number of experimental data, i.e. results for the B -> K1 gamma and B -> K* gamma radiative decays and the branching ratios for B -> pion+rho, pion+K*, K+rho, K+pion non leptonic decays. In this way we are able to make predictions on several B -> P A decays that might be used as a guide for experimental researches of these decays and as tests of factorization.

hep-ph↗