“Recommended” cross sections for electron collisions with molecules

Abstract

The procedures for constructing recommended sets of cross sections for electron scattering on molecules are described. Possible sources of errors in total and partial cross section measurements are discussed. Examples when the theory successfully supports and/or substitutes measurements are given. The target molecules discussed comprise CH4, C2H2, NF3, N2O, NO2 and H2O. 1 Databases Closer and closer deadlines for the peaceful use of thermonuclear energy [1], recent discoveries in astrochemistry [2] and the demands of studies using technological plasmas [3] have combined to trigger renewed interest in electron-molecule scattering. Numerous recommended sets of cross sections for electron scattering on atoms and molecules are available in the literature and on the internet. These cross section sets usually evolved from national centers of research.

Cross Sections for Electron Collisions with H2O

“…Long-standing contradictions on elastic scattering (and therefore also the beam measurements of the momentum-transfer cross sections) got an important experimental contribution from California State University (CSU) 69 and now seem to correspond to the theoretical indications. 50 With support from the theory, 50 we solve the earlier ambiguities in defining total and EMT cross sections; 19 see Fig. 7.…”

“…[15][16][17][18] However, in some cases, significant differences appear in outcomes of those works; see our detailed comparison in Ref. 19. The differences in the "recommended" sets of cross sections result not only from alternative methodologies but also from different definitions of cross sections, as is discussed further in Sec.…”

Total Cross Sections for Electron and Positron Scattering on Molecules: In Search of the Dispersion Relation

“…At very low energies, swarm measurements, especially in gas mixtures, obtain self-consistent sets of partial cross sections, also for rotational and vibrational excitations [11]. However, as discussed for H 2 O (e.g., reference [12]), such sets may not be unique. Good agreements (e.g., within few per cent) exist for ionization cross sections [13].…”

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.…”