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The interaction between electrons and methane is studied with a particular focus on describing the dynamics of elastic and electronic excitation processes under the influence of the multichannel coupling effects. Elastic and electronically inelastic integral and differential cross sections are reported. These cross sections were calculated with the Schwinger multichannel method implemented with norm-conserving pseudopotentials within the minimal orbital basis for single-configuration interaction approach with up to 181 open channels. While an excellent agreement with previously published data is found in the elastic channel, the comparisons involving electronic excitation cross sections reveal significant discrepancies. Furthermore, the lack of reliable experimental data regarding the electronically inelastic channels hampers a more detailed analysis of the theoretical results. Additionally, total ionization and total cross sections for electron collisions with methane are also presented. By highlighting the current theoretical challenges in dealing with electron-induced electronic excitation of molecules, we seek to contribute to a deeper understanding of this scattering process and, thus, pave the way for future research. [ABSTRACT FROM AUTHOR]

Measurements of the total electron scattering cross sections (TCSs) from benzene, in the impact energy range of 1–1000 eV, are presented here by combining two different experimental systems. The first utilizes a magnetically confined electron transmission beam for the lower energies (1–300 eV), while the second utilizes a linear transmission beam apparatus for the higher energies (100–1000 eV). These cross sections have also been calculated by means of two different theoretical methods, the Schwinger Multichannel with Pseudo Potential (SMCPP) procedure, employing two different approaches to account for the polarization of the target for impact energies between 0.1 and 15 eV, and the Independent Atom Model with the Screening Corrected Additivity Rule including Interference effect (IAM-SCAR+I) paradigm to cover the 10–10 000 eV impact energy range. The present results are compared with available theoretical and experimental data, with the level of accord being good in some cases and less satisfactory in others, and some predicted resonances have been identified. In particular, we found a π* shape resonance at 1.4 eV and another feature in the energy region 4.6–4.9 eV interpreted as a π* resonance (2B2g symmetry), which is a mixture of shape and a core excited resonance, as well as a Feshbach resonance at 5.87 eV associated with the 3s (a1g) Rydberg state. A Born-type formula to extrapolate TCS values for energies above 10 000 eV is also given. This study provides a complete set of TCS data, with uncertainty limits within 10%, ready to be used for modeling electron transport applications. [ABSTRACT FROM AUTHOR]

We report the results of ab initio calculations for elastic scattering and also for excitation of individual electronic states of para-benzoquinone (pBQ) by the impact of low-energy electrons. The calculations for elastic scattering were performed with the Schwinger multichannel method implemented with pseudopotentials (SMCPP) in the static-exchange (SE) plus polarization (SEP) approximation for energies up to 50 eV. The assignments for the resonance spectrum obtained in this study are, in general, in good agreement with previous results available in the literature. For electronic excitation by electron impact, the SMCPP method with N energetically open electronic states (Nopen), at either the static-exchange (Nopench-SE) or the static-exchange-plus-polarisation (Nopench-SEP) approximation, was employed to calculate the scattering amplitudes using a channel coupling scheme that ranges from the 1ch-SEP up to the 89ch-SE level of approximation, depending on the energy of interest. Integral cross sections (ICSs) and differential cross sections (DCSs) were obtained for incident electron energies lying between 15 eV and 50 eV. The study focuses on the influence of multichannel coupling effects for electronically inelastic processes, more specifically, on how the number of excited states included in the open-channel space impacts upon the convergence of the cross sections at intermediate and higher energies. In particular, we found that the magnitude of DCS and ICS results for electronic excitation decreases as more channels are included in the calculations. To the best of our knowledge, there are no other experimental or theoretical ICS or DCS results for excitation into individual electronic states of pBQ available in the literature between 15 and 50 eV against which we might compare the present calculations. [ABSTRACT FROM AUTHOR]

We report absolute experimental integral cross sections (ICSs) for electron impact excitation of bands of electronic-states in furfural, for incident electron energies in the range 20-250 eV. Wherever possible, those results are compared to corresponding excitation cross sections in the structurally similar species furan, as previously reported by da Costa et al. [Phys. Rev. A 85, 062706 (2012)] and Regeta and Allan [Phys. Rev. A 91, 012707 (2015)]. Generally, very good agreement is found. In addition, ICSs calculated with our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arise due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section for electron-furfural scattering. Where possible, those calculated IAM-SCAR+I ICS results are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, but only for the band I and band II excited electronic states, we also present results from our Schwinger multichannel method with pseudopotentials calculations. Those results are found to be in good qualitative accord with the present experimental ICSs. Finally, with a view to assembling a complete cross section data base for furfural, some binary-encounter-Bethe-level total ionization cross sections for this collision system are presented. [ABSTRACT FROM AUTHOR]

We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (C5H4O2). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of C5H4O2. The measurements were carried out at energies in the range 20-40 eV, and for scattered-electron angles between 10° and 90°. The energy resolution of those experiments was typically ~80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6-50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail. [ABSTRACT FROM AUTHOR]

We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C6H5OH). The measurements were carried out at incident electron energies in the range 15-40 eV and for scattered-electron angles in the range 10-90°. The energy resolution of those measurements was typically ~80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C6H5OH molecule by electron impact. [ABSTRACT FROM AUTHOR]