Elastic electron scattering from sulfur hexafluoride

Abstract

Absolute differential cross sections for elastic scattering of electrons from sulfur hexafluoride (SF 6 ) have been measured at 11 incident energies between 2.7 and 75 eV and for scattering angles between 10 • and 130 • . The magnetic angle-changing device of Read and coworkers has been used to extend these measurements to backward angles (130 • -180 • ) for incident energies below 15 eV. The measurements reveal some substantial differences with several previous determinations and a reasonably good level of agreement with a recent close-coupling calculation.

Low-energy electron collisions with sulfur hexafluoride, SF6

“…Calculations employing more extensive coupling schemes would be useful in assessing the latter possibility. Under the circumstances, we can at least say that our calculations suggest that in the low-energy, near-threshold region, which is of primary importance in modeling of low-temperature plasmas, the 1 1,3 T 1u excitations appear to be the most important among those studied here.…”

“…10͒. Although calculation and experiment both produce forwardpeaked cross sections that are of the same order of magnitude and much larger than those for 1 1,3 T 1g shown in Fig. 9, the differences between theory and experiment are considerable.…”

“…For the 11.6 eV process that Trajmar and co-workers assign as 1 1,3 T 1u , agreement is at best qualitative ͑Fig. 10͒.…”

“…Based on those results, we chose to calculate excitation cross sections for the five lowest triplet states, namely, 1 3 T 1g , 1 3 T 1u , 1 3 T 2u , 1 3 T 2g , and 1 3 E g , and for each of the corresponding singlets except 1 1 E g , which was excluded because its SECI threshold ͑15.23 eV͒ lay well above the 1 3 E g threshold. All of the states considered here arise from promotion of a fluorine lone-pair electron into the lowest unoccupied molecular orbital ͑LUMO͒, which is the S-F antibonding 6a 1g orbital.…”

Elastic Cross Sections for Electron Collisions with Molecules Relevant to Plasma Processing

“…45 In the work of Cho et al 40,41 a magnetic angle-changing device was employed in conjunction with an electron spectrometer to measure the cross sections to backward angles at low impact energies. While these results show somewhat scattered distributions, Rohr, 42 Sakae et al 7 and Cho et al 40,41 show remarkably good agreement at those electron energies for which they overlap. We would also like to note that there is a quite recent measurement by Bhushan et al 46 for the energy region from 50 to 500 eV, which is pretty much overlapped with that of Sakae et al, and both measurements agree with each other within the uncertainties in the energy region of the current interest.…”