Rotational and vibrational excitation in the large-angle scattering ofNa+ions fromN2molecules

Differential scattering of ${\mathrm{Na}}^{+}$ ions from ${\mathrm{N}}_2$ molecules was studied at laboratory energies of 100≤$E_{\mathrm{lab}\mathrm{\le }350}$ eV and scattering angles of 15°≤θ≤45°. The energy-loss spectra were measured with the time-of-flight technique. The experimental results were analyzed by the classical trajectory calculation. The spectra measured at small angles show a typical double-peak structure, while at large angles the spectra are composed of the three peaks. The triple-peak structure can be explained in terms of the rainbow effect on the angular momentum transfer mechanism, by taking into account the direction of the final rotational angular momentum vector. A drastic structural change of the energy-loss spectra was observed around the reduced scattering angle of τ=8 keV deg, independent of the collision energy. This can also be attributed to the rainbow effect arising from vibrational excitation.