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

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2016
Author Regeta Khrystyna , Allan Michael , Winstead Carl , McKoy Vincent, Mašín Zdeněk, Gorfinkiel Jimena D.,
Project Chemical and Physical Processes from Electron-Molecule Interactions
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Original article (peer-reviewed)

Journal Journal of Chemical Physics
Volume (Issue) 144
Page(s) 024301
Title of proceedings Journal of Chemical Physics
DOI 10.1063/1.4937790

Open Access


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 2A2, A2B1, and B2B1 shape resonances. As a consequence of superposition of coherent resonant amplitudes with background scattering the B 2B1 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.