Internal and translational energy of sputtered silver dimers: a molecular dynamics study

The ejection of Ag₂ molecules from a (111)-silver surface bombarded by normally incident Ar⁺ ions was studied by a molecular dynamics simulation using a many-body embedded-atom interaction potential. First, the dependence of the translational energy distribution on the polar ejection angle was calculated and compared to corresponding experimental results. Then, the internal energy distribution as well as the vibrational and rotational state distributions of sputtered Ag₂ dimers were calculated and their correlation with the primary ion energy, the translational energy and the polar ejection angle was examined. It is found that the rotational-vibrational population can be well approximated by Boltzmann distributions revealing vibrational and rotational temperatures of 3000-5000 K and 8000-10000 K, respectively. The dependence of T_vib and T_rot on the primary ion energy, the translational energy and the polar ejection angle of the sputtered molecules is shown to be relatively weak.