Atomic data for spectral analysis
Collisional excitation and ionization cross sections suitable to highly excited states of the target atom at low and intermediate kinetic energy of the scattering particle have been derived following the semiclassical Impact Parameter approximation. An analytical expression for cross section involving transitions with $\Delta l > 1$ has been obtained when the semiclassical requirement and the Ehrhardt conditions are valid. The analytical cross sections are explicit functions of the initial quantum number of the target atom, the incident velocity of the colliding particle and $\Delta n$ (for bound-bound transitions), allowing a generalization to any transition needed in a spectral modeling code. The cross sections obtained with the Impact Parameter approximation present a close agreement with previous theoretical results for dipole and quadrupole ($\Delta l$ = 2) cross sections of bound-bound transitions. Results of octupolar ($\Delta l$ = 3) cross sections are also given for $\Delta n$ = 1 and $\Delta n$ = 2 and a wide range of incident energies. The results indicate that the cross sections corresponding to transitions with $\Delta l > 1$ are significant up to incident energies about 100 times the transition energy. The Impact Parameter cross sections for bound-free transitions present a very good agreement with experimental values, in particular at low incident energies.