Absolute total non-dissociative and partial dissociative cross sections of pyrimidine were measured for electron impact energies ranging from 70 to 400 eV and for proton impact energies from 125 up to 2500 keV. MOs ionization induced by coulomb interaction were studied by measuring both ionization and partial dissociative cross sections through time of flight mass spectrometry and by obtaining the branching ratios for fragment formation via a model calculation based on the Born approximation. The partial yields and the absolute cross sections measured as a function of the energy combined with the model calculation proved to be a useful tool to determine the vacancy population of the valence MOs from which several sets of fragment ions are produced. It was also a key point to distinguish the dissociation regimes induced by both particles. A comparison with previous experimental results is also presented.
The multiple ionization of Kr and Xe by protons has been analysed in detail within the independent particle model. The dependence of the multiple ionization cross sections on the values of the ionization probabilities has been investigated for each target subshell and the most relevant pathways for final quadruple to sextuple ionization are identified. The influence of post-collisional ionization probabilities due to Auger-like effects after the removal of one or more inner-shell target electrons has also been considered. It has been observed that, for large final charge states of the target, deep-core ionization plays an important role, due to the increase in the number of ejected electrons arising from post-collisional effects.
We present in detail an alternative experimental set-up and data analysis, based on the electron-recoil ion and recoil ion-projectile coincidence techniques, that enable the measurement of partial pure ionization and partial charge exchange cross sections for an effusive gas jet set-up, where the absolute target density and recoil ion efficiency cannot be measured directly. The method is applied to the ionization of helium atoms due to collision with partially stripped C(3 +) projectiles. In order to check the method, the results are compared to data available in the literature where the target density and recoil ion detection efficiency were measured directly. The pure ionization channel is compared to the electron capture channel.
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