Shape resonances, virtual state, and Ramsauer-Townsend minimum in the low-energy electron collisions with benzene

Abstract

In this work, we revisit the low-energy electron scattering by benzene. We employed the Schwinger multichannel method implemented with pseudopotentials to carry out systematic cross section calculations with different schemes of polarization for the resonant and the totally symmetric irreducible representations within the D symmetry group. We present integral and differential cross sections for incident electron energies up to 12 eV and discuss the shape resonances and the presence of a Ramsauer-Townsend minimum and a virtual state in the former. We also discuss the relation of these physical phenomena with the different schemes of the polarization effects employed in our calculations. Finally, the comparison of our calculated integral and differential cross sections with the available data from the literature suggests improvement in the agreement between theory and experiment.

Experimental and theoretical analysis for total electron scattering cross sections of benzene

“…In this application, this allows for two different levels of approach to include polarization effects (SEP1 and SEP2). 28 Within this representation, shape resonances can be identified from the integral elastic cross section profile, which we reiterate in this case has been calculated for very low impact energies from 0 to 15 eV. The IAM-SCAR+I method is a well-established calculation procedure which is based on an independent atom representation but considers the molecular geometry to account for the overlapping of the atomic cross sections and additionally considers multiple scattering interference effects.…”

“…Singh et al 27 also included results of TCS calculations for electrons scattering off benzene from 10 to 5000 eV impact energies in their benzene derivatives analysis by using a modified spherical complex optical potential (MSCOP) method. Recently, Barbosa and Bettega 28 employed the Schwinger multichannel method implemented with pseudopotentials (SMCPP) to carry out systematic elastic cross section calculations including a complete resonance analysis to identify any temporary anion formation and the presence of a virtual state and a Ramsauer-Townsend minimum. Finally, Prajapati et al 29 computed the electron scattering TCS for benzene by using two different methods.…”

“…For the lower energies (1-300 eV), we used a magnetically confined electron transmission beam system with an energy resolution of about 200 meV, while for the higher energies (100-1000 eV), a modified transmission-beam system with improved angular resolution (<10 −5 sr) has been utilized. Concerning our theoretical data, we have re-examined our previous SMCPP calculation 28 in the energy range where they can be considered to be roughly equivalent to the TCS (0-5 eV). Note that in this range, below the electronic excitation threshold, the rotational excitation cross sections are much lower in magnitude than the elastic cross sections, and the electron attachment cross sections are accounted by the SMCPP calculation as resonances over the integral elastic cross sections.…”

Theoretical study on positron scattering by benzene over a broad energy range

“…All calculations were carried out in the optimized geometry of benzene (shown in Fig. 1), obtained previously in our work on electron scattering by the same molecule [18]. The DZV++(2d, 1p) basis set as implemented in the package GAMESS [19] was used in the bound-state and scattering calculations.…”

Double and Triple Differential Cross Sections for Single Ionization of Benzene by Electron Impact

“…Benzene (C 6 H 6 ) is the simplest aromatic hydrocarbon, and therefore acts as a reference model for understanding the physico-chemical properties of a vast set of biologically relevant molecules. Nevertheless, although one finds in the literature [ 7 , 8 , 9 , 10 , 11 ] (and references therein) several studies on electron interactions with benzene, detailed investigations of the electron-impact ionization dynamics have not been performed to date, as far as the authors are aware. Nonetheless, different studies on the ionization and fragmentation dynamics of benzene produced by intense laser fields [ 12 , 13 , 14 ] or excited metastable atoms [ 15 ] can be found in the literature.…”