Theoretical study of multiple ionization of diatomic molecules by ion impact

C.A. TACHINO; M.E. GALASSI; R.D. RIVAROLA

Belfast, Irlanda

Conferencia; 13th International Conference on the Physics of Highly Charged Ions (HCI); 2006

The study of multiple ionization in ion-molecule collisions is a subject of principal interest in many areas of physics, astrophysics, hadrontherapy and radiobiology. In particular, N2, CO and O2 gases are present in planetary and cometary atmospheres, where the solar wind and cosmic rays stimulate the multi-electron emission. These gases are also present in ionization chambers used to calibrate accelerators employed for radiotherapy. Stimulated by this interest, in the present work we calculate differential and total multiple ionization cross sections for impact of ions on the above mentioned molecules, at intermediate and high collision energies. To this end, we work within the framework of the Independent Particle Model (IPM), where the multiple ionization probabilities are calculated using binomial distributions [1]. The impact parameter probabilities for single-ionization are obtained applying different approximations: the Exponential (EM) [2] and the Continuum Distorted Wave -Eikonal Initial State (CDW-EIS) [3] models. The molecules are described as separated atoms or using molecular wavefunctions. The influence of the molecular orientation on differential cross sections is analyzed. An adequate description of existing experimental data is obtained. At high enough impact energies, the role played by post-collisional mechanisms in total cross sections is discussed. References [1] M. M. Sant’Anna, E. C. Montenegro, and J. H. McGuire, Phys. Rev. A 58, 2148 (1998). [2] C. Caraby, A. Cassimi, L. Adoui, and J. P. Grandin, Phys. Rev. A 55, 2450 (1997), and references therein. [3] M. E. Galassi, R. D. Rivarola, M. Beuve, G. Olivera, and P. Fainstein, Phys. Rev. A 62, 022701 (2000).