Contribution of molecular orbital promotion to the electronic stopping cross section at slow atom solid collisions

The autoionization states formation due to MO promotion during collisions of keV-energy ions with solids produces a dominant contribution to inelastic energy losses and, accordingly, to the electronic stopping powers dE/dx. The correlations of emitted electron numbers 8 with the values of inelastic energy losses Q are shown. When corresponding distances of closest approach are reached, the MO orbital promotion produces a stepwise increase in values of Q and 8. Based on the measured ionization cross-sections and Q values, electronic stopping powers can be calculated. For the case when such measurements are not available, the scaling for the ionization cross section in the case of K, L and M shell excitation can be used. We have proposed a new model for calculating electronic stopping power in which the formation of autoionization states in atomic collisions makes a dominant contribution to the inelastic energy loss and ionization of colliding atoms. Using data on the values of energy losses and ionization cross sections, it is possible to calculate the values of electronic stopping. The model predicts the threshold character of the dE/dx dependence versus the collision velocity and an increase in inelastic energy losses at the collision energies at which the threshold for the corresponding MO promotion occurs.