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Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory

Regeta, Khrystyna and Allan, Michael and Winstead, Carl and McKoy, Vincent and Mašín, Zdeněk and Gorfinkiel, Jimena D. (2016) Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory. Journal of Chemical Physics, 144 (2). Art. No. 024301. ISSN 0021-9606.

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We measured differential cross sections for elastic (rotationally integrated) electron scattering on pyrimidine, both as a function of angle up to 180∘ at electron energies of 1, 5, 10, and 20 eV and as a function of electron energy in the range 0.1–14 eV. The experimental results are compared to the results of the fixed-nuclei Schwinger variational and R-matrix theoretical methods, which reproduce satisfactorily the magnitudes and shapes of the experimental cross sections. The emphasis of the present work is on recording detailed excitation functions revealing resonances in the excitation process. Resonant structures are observed at 0.2, 0.7, and 4.35 eV and calculations for different symmetries confirm their assignment as the X^2A^2, A^2B_1Ã^2B_1, and B˜2B1B̃2B1 shape resonances. As a consequence of superposition of coherent resonant amplitudes with background scattering the B^2B_1 shape resonance appears as a peak, a dip, or a step function in the cross sections recorded as a function of energy at different scattering angles and this effect is satisfactorily reproduced by theory. The dip and peak contributions at different scattering angles partially compensate, making the resonance nearly invisible in the integral cross section. Vibrationally integrated cross sections were also measured at 1, 5, 10 and 20 eV and the question of whether the fixed-nuclei cross sections should be compared to vibrationally elastic or vibrationally integrated cross section is discussed.

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Additional Information:© 2016 AIP Publishing. Received 18 September 2015; accepted 24 November 2015; published online 8 January 2016. This research is part of Project No. 200020-144367/1 of the Swiss National Science Foundation and of the COST Action No. CM1301 CELINA. This material is based in part upon work by C.W. and V.M. supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, under Award No. DE-FG02-97ER14814. C.W. and V.M. also acknowledge use of the Jet Propulsion Laboratory’s Supercomputing and Visualization Facility. Initial R-matrix calculations were performed as part of the EPSRC funded UK-RAMP Project. Z.M. and J.D.G. acknowledge the support of the ARCHER eCSE01-013 project and the use of the VULCAN computer cluster at the Max-Born Institute.
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)200020-144367/1
Swiss National Science Foundation (SNSF)CM1301 CELINA
Department of Energy (DOE)DE-FG02- 97ER14814
Engineering and Physical Sciences Research Council (EPSRC)UNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20160125-110714256
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Official Citation:Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory Khrystyna Regeta, Michael Allan, Carl Winstead, Vincent McKoy, Zdeněk Mašín and Jimena D. Gorfinkiel J. Chem. Phys. 144, 024301 (2016);
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63930
Deposited By: Ruth Sustaita
Deposited On:25 Jan 2016 22:23
Last Modified:03 Oct 2019 09:33

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