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

Here, 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 $$\sim\atop{\chi}$$ 2A 2, $$\sim\atop{A}$$ 2B 1, and $$\sim\atop{B}$$ 2B 1 shape resonances. As a consequence of superposition of coherent resonant amplitudes with background scattering the $$\sim\atop{B}$$ 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.
Authors:
 [1] ; ORCiD logo [1] ; ORCiD logo [2] ;  [2] ;  [3] ;  [4]
  1. Univ. of Fribourg, Fribourg (Switzerland)
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  3. Max-Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Berlin (Germany)
  4. The Open Univ., Milton Keynes (United Kingdom)
Publication Date:
Grant/Contract Number:
FG02-97ER14814
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 2; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
California Inst. of Technology (CalTech), Pasadena, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1468475
Alternate Identifier(s):
OSTI ID: 1234269

Regeta, Khrystyna, Allan, Michael, Winstead, Carl, McKoy, Vincent, Mašín, Zdeněk, and Gorfinkiel, Jimena D. Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory. United States: N. p., Web. doi:10.1063/1.4937790.
Regeta, Khrystyna, Allan, Michael, Winstead, Carl, McKoy, Vincent, Mašín, Zdeněk, & Gorfinkiel, Jimena D. Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory. United States. doi:10.1063/1.4937790.
Regeta, Khrystyna, Allan, Michael, Winstead, Carl, McKoy, Vincent, Mašín, Zdeněk, and Gorfinkiel, Jimena D. 2016. "Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory". United States. doi:10.1063/1.4937790. https://www.osti.gov/servlets/purl/1468475.
@article{osti_1468475,
title = {Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory},
author = {Regeta, Khrystyna and Allan, Michael and Winstead, Carl and McKoy, Vincent and Mašín, Zdeněk and Gorfinkiel, Jimena D.},
abstractNote = {Here, 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 $\sim\atop{\chi}$2A2, $\sim\atop{A}$2B1, and $\sim\atop{B}$2B1 shape resonances. As a consequence of superposition of coherent resonant amplitudes with background scattering the $\sim\atop{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.},
doi = {10.1063/1.4937790},
journal = {Journal of Chemical Physics},
number = 2,
volume = 144,
place = {United States},
year = {2016},
month = {1}
}