Triple-differential cross sections for the ionization of thymine by electrons and positrons

We apply the second Born approximation and the BBK methods to study triple-differential cross sections for the ionization of valence orbitals of a thymine molecule by electrons and positrons. Calculations have been performed for a coplanar geometry at an incident energy of 250 eV and an ejected-electron energy of 20 eV, while the angle of scattering is fixed at 10°. We use an accurate single-centre wavefunction for the initial state of the target and the well-known CNDO model. The present second Born approximation (with the single-centre wavefunction for the initial state) and the BBK model (with the CNDO model) yield cross sections in good agreement with the recent experimental data for electron impact. In the case of positron impact, we find that the contribution of the second term of the Born series is not insignificant for the present kinematics.