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• Excitations of H2 by positron impact

  J L S Lino

  010401 1–6

  2023-01-03

  Abstract:

  In this paper, we present a theoretical study of scattering cross sections for positron impact of electronic states of hydrogen molecule (H₂) using the scaling Born positron (SBP) approach. Cross sections to low-lying electronic states, B¹∑⁺_u, C¹П_u, B´¹ ∑⁺_u, and D¹П_u are investigated. In an earlier theoretical effort [J.L.S.Lino, Rev. Mex. Fisica 62 (2016) 596], an application of the SBP approach for the X¹∑⁺_g - > B¹∑⁺_u electronic excitation of the H₂ molecule, gave cross sections with reasonable qualitative agreement with experimental data [J.P.Sullivan et. al., Phys.Rev.Lett.87,073201 (2001)]. However, recent studies for the excitation of the B¹∑⁺_u state by positron impact showed that this electronic state still demand of a refined degree of description of the quality of the cross sections (Weiss et. al., Eur. Phys. J. D (2018) 72). The purpose of this work was to reexamine the B¹∑⁺_u state and verify the quality of the numerical convergence of SBP method and extend the investigation to other states. The possibility to estimate a indirect contribution of multichannel effects ( three states considering the ground X¹, B¹∑⁺_u and E,F¹∑⁺_u state) are introduced within the SBP context. For the first time, integral cross sections to these new states using the SBP approach are reported. In the absence of the experimental data and theoretical developments, comparisons are made with analogous electron scattering.

   

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  DOI: https://doi.org/10.31349/RevMexFis.69.010401

• Electronic excitation of atoms by positron impact using the scaling Born approach

  AOE Lino

  598-602

  2018-10-31

  Abstract:

  We consider the efficacy of the scaling Born positron (SBP) approach, in calculating reliable integral cross sections (ICS) for positron impact excitation of electronic states in atoms. We will demonstrate, using specific examples as H, He, Hg, and Mg, that this relatively simple procedure can generate quite accurate ICS when compared with more sophisticated methods. In the absence of the experimental data, comparisons are made with analogous electron scattering.

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  DOI: https://doi.org/10.31349/RevMexFis.64.598

• Electronic excitation of C6H6 by positron impact

  J. L. S. Lino

  188-192

  2021-07-15

  Abstract:

  Experiments on electronic excitation of molecules using positron as incident particle have shown much larger cross sections than in the electron scattering case.  The comprehension of these inelastic processes represent a great challenge and only few studies on electronic excitation of molecules are discussed in the literature. For example, for the C₆H₆ molecule experimental and theoretical calculations are not in a very advanced state same for electron scattering case (Benzene represent a simplest aromatic hydrocarbon and very important chemical compound due to its role as a key precursor in process pharmaceutical). Recent experiments on electronic excitation of C₆H₆ (¹B_1u, and ¹E_1u electronic states) using electron as incident particle are available by Kato et al (J.Chem.Phys.134 134308(2011)). Motivated by their experiments we have taken up the task to investigate the same electronic excitation of C₆H₆ using positron as incident particle.  For the first time, integral cross sections in e⁺ - C₆H₆ (¹B_1u, and ¹E_1u electronic states) using the scaling Born positron (SBP) approach are reported and in the absence of the experimental data and developments theoretical, comparisons are made with analogous electron scattering.

  Keywords: Born, positron, scaling

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  DOI: https://doi.org/10.31349/RevMexFis.67.188

• Scaling of plane-wave born cross sections for positron-impact excitations of H$₂$

  J.L.S. Lino

  596-599

  2016-01-01

  Abstract:

  We report an application of the scaling method to plane-wave Born cross sections (Y.K. Kim, Phys. Rev. A 64 (2001) 032713) using positron-impact excitation of molecules. Cross sections are obtained for positron-H$_2$ ($X^1 \Sigma_{g}^{+}$ \raisebox{-.3ex}[0cm][0cm]{-}$> B^1 \Sigma_u^+$, $ C^1 \Pi_u $) and the results are found to be in reasonable agreement with results experimental.

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  DOI: https://doi.org/10.31349/RevMexFis.62.6.596

• Electronic excitation of H$_2$, CO, and N$_2$ by positron impact

  J.L.S Lino.

  303-307

  2017-07-01

  Abstract:

  In this paper we present results for positron impact excitation of electronic states of H$_2$ (x$^1 \sum_{g}^{+} \raisebox{-.2ex}[0cm][0cm]{-} \hspace{-5pt}> $ B$^1 \sum_u^+ $, C$^1 \Pi u$), CO(X$^1 \sum_g \rightarrow $ a$^1 \Pi_g$), and, N$_2$(X$^1 \sum_g \rightarrow $ a$^1 \Pi_g$) using the scaling of plane wave Born cross sections. This method was originally proposed by Kim (Phys.Rev.A64032713(2001)) to electron scattering and adapted by Lino (Chin. J. Phys. 50 (2016) 223.) for positron scattering. Integral cross sections calculations are reported using this new method. For H$_2$ molecule our cross sections exhibit results comparable to the sophisticated theories, and experimental data. For isoelectronic molecules CO, and N$_2$ the results are compared to the ab initio Schwinger multichannel (SMC) method. For positron-CO scattering our model is very reasonable when compared with SMC method and as expected for positron-N$_2$ scattering, our results, as well as SMC method, failed to reproduce some structure observed by experimentalists. A important observation using the scaling plane wave Born for positron scattering is that the method is comparable to more sophisticated theories indicating the possibility of rapid and reliable calculations of excitation cross sections.

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  DOI: https://doi.org/10.31349/RevMexFis.63.4.303