Screening corrections for the interference contributions to the electron and positron scattering cross sections from polyatomic molecules

Total electron-scattering cross sections from pyridine molecules in the energy range 1–200 eV

“…Since the main contribution to this correction comes from the rotational excitation cross section we can conclude that our free rotating electric dipole representation based on the Born approximation to calculate dipole-induced rotational excitation cross sections reproduces the present experimental conditions well in the energy range 10-200 eV. This also indicates that interference effects affecting mainly the forward elastic scattering amplitudes [7] should be considered by independent atom calculations to properly agree with accurate integral cross-section measurements. Below 10 eV we have found reasonable agreement with the SMC [4] calculation in terms of resonance positions corresponding to the trapping of an electron in two of the three π * orbitals of pyridine at 1.2-1.6 and 4-5.5 eV, respectively.…”

“…[6] are still affecting their results. An important motivation for measuring accurate TCSs is to check the consistency of the recently incorporated interference effects [7] with our IAM-SCAR calculation [5]. The significant permanent dipole moment (2.2 D [10]) of pyridine complicates this comparison at the elastic scattering level, especially for the lower energies where dipole rotational excitations are dominant.…”

“…They represent the sum of the partial crosssection contributions from all scattering channels which are open at a given energy and therefore they are used as reference values to evaluate the completeness of a data set. In the case of pyridine, we have recently published experimental TCS values [6] for impact energies ranging from 10 to 1000 eV as measured with a double-spectrometer transmission-beam technique, together with an update of our previous Independent Atom Model with the Screening Corrected Additivity Rule (IAM-SCAR) calculation [5] by incorporating the effect of interferences in the elastic scattering cross sections (IAM-SCAR+I) [7]. Although those experimental results confirmed the reliability of the updated calculation by showing better agreement when interference terms are included, they are systematically lower than the calculated results, suggesting that new measurements with different techniques should be carried out to identify possible systematic errors.…”

Theoretical study on positron scattering by benzene over a broad energy range

“…where the momentum transfer is q = k f − k i and the atomic positions are given by r i . In this calculation we incorporate the recent improvement of considering interference effects [28]. This updated version is known as IAM-SCAR+I and basically provides the molecular differential cross section (dσ elastic molecule /dω) as a combination of the multicenter atomic amplitudes given by…”

Magnetically confined electron beam system for high resolution electron transmission-beam experiments

“…For this purpose, we have used our independent atom model with screened corrected additivity rule and interference effects (IAM-SCAR+I) method which has been described in detail elsewhere. [17][18][19] For an electron energy resolution of 200 meV, the missing angles given by Eq. (9) range from 6 • to 29 • for incident energies from 1 to 300 eV.…”