Absolute total cross sections for electron detachment have been measured for collisions of ${\mathrm{Na}}^{\mathrm{-}}$ and ${\mathrm{K}}^{\mathrm{-}}$ with rare gases at relative collision energies ranging from a few eV to about 200 eV. These alkali-metal anions, which are characterized by angularly correlated ${\mathrm{ns}}^2$ electrons, are observed to be extremely stable with respect to collisional electron detachment. For the ${\mathrm{Na}}^{\mathrm{-}}$-Ne and ${\mathrm{K}}^{\mathrm{-}}$-Ar,Kr,Xe systems, the salient features of the detachment cross sections are described by a simple curve-crossing model. Cross sections for ${\mathrm{Na}}^{\mathrm{-}}$-He,Ar,Kr,Xe and ${\mathrm{K}}^{\mathrm{-}}$-He,Ne remain small (<0.5 A${̊}^2$) throughout the energy range studied. Striking similarities are observed between the energy dependence of these detachment cross sections and that of the cross sections for projectile excitation which results from neutral-alkali-metal–rare-gas collisions.

• Received 7 February 1985

DOI:https://doi.org/10.1103/PhysRevA.32.144