Threshold photodetachment in a repulsive potential
  We report on the first experimental observation of a new threshold behavior observed in the 5g partial channel in photodetachment of K-. It arises from the repulsive polarization interaction between the detached electron and the residual K(5g) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5g) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme. 
Anton O. Lindahl, Johan Rohl\'en, Hannes Hultgren, Igor Yu. Kiyan,   David J. Pegg, C. Wesley Walter, and Dag Hanstorp
physics.atom-ph