TY - JOUR

T1 - Correlation-polarization effects in electron/positron scattering from acetylene

T2 - A comparison of computational models

AU - Franz, J.

AU - Gianturco, F. A.

AU - Baluja, K. L.

AU - Tennyson, J.

AU - Carey, R.

AU - Montuoro, R.

AU - Lucchese, R. R.

AU - Stoecklin, T.

AU - Nicholas, P.

AU - Gibson, T. L.

N1 - Funding Information:
J.F., J.T. and K.L.B. acknowledge funding from both EPSRC and the Royal Society through their India–UK exchange program. J.F. thanks the EIPAM network of the European Science Foundation (ESF) for the award of a fellowship at the beginning of the present work. F.A.G. further thanks the CASPUR Consortium for the availability of computational time for the present project. This work was also supported by the Robert A. Welch Foundation (Houston, TX) under grant A-1020.

PY - 2008/2

Y1 - 2008/2

N2 - Different computational methods are employed to evaluate elastic (rotationally summed) integral and differential cross sections for low energy (below about 10 eV) positron scattering off gas-phase C2H2 molecules. The computations are carried out at the static and static-plus-polarization levels for describing the interaction forces and the correlation-polarization contributions are found to be an essential component for the correct description of low-energy cross section behavior. The local model potentials derived from density functional theory (DFT) and from the distributed positron model (DPM) are found to produce very high-quality agreement with existing measurements. On the other hand, the less satisfactory agreement between the R-matrix (RM) results and measured data shows the effects of the slow convergence rate of configuration-interaction (CI) expansion methods with respect to the size of the CI-expansion. To contrast the positron scattering findings, results for electron-C2H2 integral and differential cross sections, calculated with both a DFT model potential and the R-matrix method, are compared and analysed around the shape resonance energy region and found to produce better internal agreement.

AB - Different computational methods are employed to evaluate elastic (rotationally summed) integral and differential cross sections for low energy (below about 10 eV) positron scattering off gas-phase C2H2 molecules. The computations are carried out at the static and static-plus-polarization levels for describing the interaction forces and the correlation-polarization contributions are found to be an essential component for the correct description of low-energy cross section behavior. The local model potentials derived from density functional theory (DFT) and from the distributed positron model (DPM) are found to produce very high-quality agreement with existing measurements. On the other hand, the less satisfactory agreement between the R-matrix (RM) results and measured data shows the effects of the slow convergence rate of configuration-interaction (CI) expansion methods with respect to the size of the CI-expansion. To contrast the positron scattering findings, results for electron-C2H2 integral and differential cross sections, calculated with both a DFT model potential and the R-matrix method, are compared and analysed around the shape resonance energy region and found to produce better internal agreement.

KW - 31.25.v

KW - 34.80.Bm

KW - 34.85.+x

KW - Computed angular distributions for e/e scattering

KW - Electron-molecule scattering

KW - Molecular gases

KW - Positron-molecule scattering

KW - Quantum calculations

UR - http://www.scopus.com/inward/record.url?scp=39949084470&partnerID=8YFLogxK

U2 - 10.1016/j.nimb.2007.12.019

DO - 10.1016/j.nimb.2007.12.019

M3 - Article

AN - SCOPUS:39949084470

VL - 266

SP - 425

EP - 434

JO - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

JF - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

SN - 0168-583X

IS - 3

ER -