Electron collisions with formic acid

Abstract

We report elastic, electronically inelastic, total ionization and total cross sections for the scattering of electrons by trans-formic acid. The calculations of the elastic and electronically inelastic cross sections were performed with the Schwinger multichannel method implemented with norm-conserving pseudopotentials. The electronically inelastic calculations were done within the minimal orbital basis for single configuration interaction approach with different multichannel coupling schemes considering from 1 up to 51 open channels, which enable us to study the influence of the multichannel coupling effects on the calculated cross sections. Polarization effects in the elastic channel were taken into account considering only the excitations related to the pairs used in the minimal orbital basis for single configuration interaction approach. We found that the magnitude of the elastic and inelastic cross sections decreases as more channels are treated as open in the scattering calculations. The calculated elastic differential cross sections present an overall good agreement with previous studies found in the literature. The elastic integral cross section presents a well-known π * shape resonance centered at 1.96 eV. The total ionization cross section was calculated with the binary-encounter-Bethe model and presents a good agreement with previous results from the literature. The total cross section was estimated using the calculated elastic, inelastic and ionization cross sections.

Cross sections for elastic electron scattering by benzene at low and intermediate energies

“…This is because we only accounted for target states below 10 eV, which should have a progressively less impact in the multichannel coupling as E 0 increases. These findings have been observed in previous applications of the SMC method to other systems [33][34][35][39][40][41][42],…”

“…This could be an unintended artifact for ignoring the continuum of ionized target states in the SMC method. In similar studies for ethanol [42] and formic acid [41], where channels lying above the IP were considered to be open, calculated elastic DCSs at higher energies also appeared underestimated with respect to experimental data. At this point, however, we cannot conclude that not properly describing the ionization is the ultimate cause of the small elastic DCSs.…”

“…The projection operator P , which projects onto the space of open channels, plays a central role in the method. Several previous studies using the SMC method have shown that allowing progressively more channels in P tends to improve the comparison with experiment [24,[34][35][36][37][38][39][40][41]. Typically, opening more channels causes the calculated elastic cross sections to decrease, thus approaching the experimental values from above, though with some overestimation.…”

“…More recently, owing to improvements in the computational code and the description of target states [42], it has been possible to significantly increase the number of open channels in scattering calculations with the SMC method, reaching a record of 431 for ethanol [42] and of 305 for benzene [33]. In these two recent applications [33,42], and also for formic acid [41], first indications of an interesting behavior showed up. In some cases, the computed elastic cross sections actually decreased "too much" when opening more channels, appearing below the experiment, inspiring important questions regarding the SMC method.…”

Molecular collisions, photoionization and dynamics: honouring Professor Vincent McKoy

“…A combined experimental and theoretical study of helium adsorption on cationic hexaphenylbenzene (HPB), a propeller-shaped molecule, was investigated [14], and molecular synthesis in ices triggered by dissociative electron attachment to carbon monoxide was presented by Schmidt et al [15]. García-Abenza and co-workers [16] reported on a complete data set for the simulation of electron transport through gaseous tetrahydrofuran in the energy range 1-100 eV as a significant attempt to understand radiation damage in biological related molecules particle track simulations, whilst Randi et al [17] described elastic, electronically inelastic, total ionization and total cross sections for the scattering of electrons by trans-formic acid. Falkowski et al [18,19], within the relevance of a model potential for computing total ionization cross sections of atoms and molecules by electron impact, reported on hydrogen, carbon, nitrogen and oxygen atoms and for hydrogen, nitrogen, water, methane and benzene molecules.…”