Low to intermediate energy elastic electron scattering from dichloromethane (CH₂Cl₂)

Abstract

We report a theoretical-experimental investigation of electron scattering by dichloromethane (CH 2 Cl 2) in the low-and intermediate energy ranges. Experimental elastic differential cross sections (DCS), in the incident electron energy range of 0.5-800eV and scattering angle range of 10°-130°, were measured using a crossed beam relative flow technique. Integral and momentumtransfer cross sections were determined from the experimental DCS. Theoretical elastic differential, integral, and momentum-transfer, as well as grand-total, and total absorption cross sections were also calculated for impact energies ranging from 0.5 to 500eV. A complex optical Hartree-Fock potential represented the electron-target interaction and a single-center expansion method combined with a Padé approximation was used to solve the scattering equations. Three resonances: a 2 A 1 C-Cl kσ * resonance centered at about 3.5eV, a 2 B 2 C-Cl kσ * resonance centered at about 5eV and a broad 2 A 1 C-H kσ * resonance at about 10eV were detected in our calculation. Further calculations of DCS were performed at an intermediate energy range of 50-800eV, using the independent-atom model in which the atomic complex optical potential and partial-wave method were used to obtain atomic scattering amplitudes. Comparisons of our experimental and theoretical data with very recent experimental and theoretical results are made.

Total cross section measurements for electron scattering from dichloromethane

“…1 are the TCS results from the previous measurements of Wan et al 14 and Karwasz et al, 15 along with theoretical IAM-SCAR+I and IAM-SCAR+I+rotations total cross sections of Krupa et al 12 and an SCOP result of 15 (green crosses) and theoretical IAM-SCAR+I (blue solid curve) 12 and IAM-SCAR+I+rotations (blue short dashed curve) 12 and SCOP (brown dotted curve) 16 results. The IAM-SCAR+I+rotations result when corrected for the "missing angle" effect (black dotted-dashed curve) 19 and the measured elastic ICSs of Hlousek et al 13 (red open circles) are also shown. Note that the uncertainties on the present data are statistical only.…”

“…Naghma et al 16 The corrected, for the "missing angle" effect, IAM-SCAR+I+rotations TCSs are also given in this figure. Finally, some recent experimental elastic ICSs of Hlousek et al 13 are also included. We note that experimental elastic ICSs, over a more restricted energy range, were also reported in the work of Krupa et al 12 Those ICSs were derived from their elastic DCSs, whose angular distributions appear to be uncorrected for the "effective path length correction factor."…”

“…As the angular distributions of Krupa et al 12 were not corrected for this, the ICSs derived from them are possibly unreliable and this is why they are not plotted here. Note that the elastic DCSs in the work of Hlousek et al 13 were all measured using a variant of the relative flow technique, [23][24][25] which, if correctly applied, cancels out any possible effective path length correction factor. We therefore believe that the elastic DCSs of Hlousek et al 13 are credible so that their ICSs are also sound and hence plotted in Fig.…”

“…As a consequence, we do not repeat that information here. In addition, both those investigations 12,13 provided excellent summaries of the currently available cross section data for electron scattering from CH 2 Cl 2 . We therefore also do not repeat those details here, except to note the previous TCS experimental results of Wan et al, 14 for energies in the range 0.18-12 eV, and the data of Karwasz et al, 15 for energies in the range 75-4000 eV.…”

“…This follows as the total cross section provides a crucial self-consistency check when one starts to form such a database for the simulations as the integral cross sections (ICSs) for all energetically open channels (e.g., elastic scattering, vibrational excitation, a) Author to whom correspondence should be addressed: g.garcia@csic.es ionisation, and so on) must add up, at a given incident electron energy, to the TCS. [8][9][10][11] With respect to the particular case of dichloromethane (CH 2 Cl 2 ), there have been two recent electron impact studies 12,13 which have detailed why a priori it is an interesting species to investigate. As a consequence, we do not repeat that information here.…”