Interaction of antiprotons with Rb atoms and a comparison of antiproton   stopping powers of the atoms H, Li, Na, K, and Rb
  Ionization and excitation cross sections as well as electron-energy spectra and stopping powers of the alkali metal atoms Li, Na, K, and Rb colliding with antiprotons were calculated using a time-dependent channel-coupling approach. An impact-energy range from 0.25 keV to 4000 keV was considered. The target atoms are treated as effective one-electron systems using a model potential. The results are compared with calculated cross sections for antiproton-hydrogen atom collisions. 
Armin L\"uhr, Nicolas Fischer, and Alejandro Saenz