Electron collisions with molecules and molecular clusters

Abstract

State-of-the art computational studies of electron collisions with molecules and small molecular clusters are illustrated with results obtained from the application of the R-matrix method and the UKRMol/UKRMol+ suites. High-level calculations of electronic excitation cross sections and core-excited resonances, mainly of core-excited shape character, show excellent agreement with experiment for mid-size molecules like pyrimidine and thiophene. Simpler calculations are paving the way for an in-depth understanding of the effect of hydration on resonance formation: how the shift in resonance energy depends on the characteristics of the hydrogen bond and the resonance being studied. Finally, applications of the software to a little studied process, interatomic coulombic electron capture are also illustrated.

Excitation and ionisation cross-sections in condensed-phase biomaterials by electrons down to very low energy: application to liquid water and genetic building blocks

“…83,84 Panels (c) and (d) represent the same as (a) and (b), but as a function of the effective number of valence electrons. 59 The straight lines in panel (c) represent the linear fittings by means of eqn (24) with the parameters given in Table 3.…”

“…Nonetheless, the scaling in the TECS is not satisfactory, neither as a function of the number of valence nor of effective electrons. However, this deficiency does not seem to arise from limitations of the model, as the calculated TECS have been shown reasonably Table 3 Slopes b for the linear dependence of the TICS and the SCS on the effective number of valence electrons, N eff , eqn (24), for different initial electron energies T, and parameters g and d for the relation of the slope b with the electron energy, eqn (25) T (eV) accurate in comparison with experimental data for water and THF vapour, as well as for solid cytosine, adenine and thymine. Thus, we attribute the less predictable behaviour of the TECS to the larger number of variables on which it depends, namely the features of the ELF (related to the number of valence electrons), but also to the values of both the electronic excitation threshold E th and the mean binding energy of outer-shell electrons B out (T), whose values cannot be, in principle, anticipated.…”

“…22 An alternative for gathering all relevant cross-sections resorts into theoretical calculations, where some very successful ab initio approaches are available for calculating both excitation and ionisation cross-sections. 23,24 However, the required tools and background are usually rather complex and not accessible for a wide audience. There are also a number of very popular semiempirical models, [25][26][27] which are easy to implement but, in return, remain generally limited to the ionisation process and/or they cannot provide the energy spectrum of the generated electrons, which is essential for following up their transport in the simulations.…”

Recent studies with electrons, positrons and positronium

“…swarm physics illustrate the current focus of the field, with several contributed topical reviews[12,16,18,22] highlighting progress made up to now. Specifically, positron and positronium scattering or structure calculations on a range of targets were reported by Barp and Arretche[1], Hervieux and Chakraborty[3], Ellis-Gibbings et al[4], Arretche et al[5], Tenfen et al[10], Seidel and Arretche[11], DeMars et al[14], Ono et al[23], and Yazejian and Straton[24].…”

“…Specifically, positron and positronium scattering or structure calculations on a range of targets were reported by Barp and Arretche[1], Hervieux and Chakraborty[3], Ellis-Gibbings et al[4], Arretche et al[5], Tenfen et al[10], Seidel and Arretche[11], DeMars et al[14], Ono et al[23], and Yazejian and Straton[24]. A comprehensive series of electron scattering, both theoretical and experimental, contributed topical reviews, covering a very wide variety of molecules, were contributed by Scarlett et al[12], Gorfinkiel[16], Song et al[18], and Lopes et al[22]. Original electron scattering articles, for a variety of scattering processes Finally, some modelling study results from Campbell et al[2], on the atmosphere of Jupiter, and Nyffenegger-Pere and Cocks[6], on plasma diagnostic opportunities from a positron beam, round out this volume.The next POSMOL conference will be held at the University of Notre Dame, Notre Dame in Indiana, the USA, on July 29th-August 1st, 2021.…”