Differential cross sections for electron-impact excitation of the electronic states of pyrimidine

Pyrimidine (C$_{4}$N$_{2}$H$_{4})$ is an important molecule, as it forms the basis of larger biomolecules, such as the DNA bases thymine, cytosine and uracil. There is a pressing demand for low-energy electron scattering data from such biological analogs in order to model radiation induced damage [1]. We therefore present the first measurements for absolute differential cross section data for low-energy electron-impact excitation of the electronic states of pyrimidine. The present measurements were performed using a crossed-beam apparatus [2] for incident electron energies ranging between 15 to 50eV while covering a 10 to 90$^{\circ}$ angular range. Here the absolute scale has been determined through a normalisation to the recently measured elastic scattering differential cross section data for pyrimidine [3]. [1] F. Ferreira da Silva, D. Almeida, G. Martins, A. R. Milosavljevic, B. P. Marinkovic, S. V. Hoffmann, N. J. Mason, Y. Nunes, G. Garcia and P. Limao-Vieira, \textit{Phys Chem Chem Phys} \textbf{12}, 6717 (2010). [2] M. J. Brunger and P. J. O. Teubner, \textit{Phys Rev A} \textbf{41}, 1413 (1990). [3] P. Palihawadana, J. Sullivan, M. Brunger, C. Winstead, V. McKoy, G. Garcia, F. Blanco and S. Buckman, \textit{Phys Rev A} \textbf{84}, 062702 (2011).