title: Absolute cross sections for electronic excitation of pyrimidine by electron impact.
abstract: We measured differential cross sections for electron-impact electronic excitation of pyrimidine, both as a function of electron energy up to 18 eV, and of scattering angle up to 180°. The emphasis of the present work is on recording detailed excitation functions revealing resonances in the excitation process. The differential cross sections were summed to obtain integral cross sections. These are compared to results of R-matrix calculations, which successfully reproduce both the magnitude of the cross section and the major resonant features. Comparison of the experiment to the calculated contributions of different symmetries to the integral cross section permitted assignment of several features to specific core-excited resonances. Comparison of the resonant structure of pyrimidine with that of benzene revealed pronounced similarities and thus a dominant role of π-π(∗) excited states and resonances. Electron energy loss spectra were measured as a preparation for the cross section measurements and vibrational structure was observed for some of the triplet states. A detailed analysis of the electronic excited states of pyrimidine is also presented.
authors.affiliation: Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland.
authors.forename: Khrystyna
authors.initials: K
authors.lastname: Regeta
authors.affiliation: Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Allan
authors.affiliation: Max-Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2A, 12489 Berlin, Germany.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Mašín
authors.affiliation: Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom.
authors.forename: Jimena D
authors.initials: JD
authors.lastname: Gorfinkiel