Phase-Interference Effects in InelasticHe++ He Collisions

In the collision ${\mathrm{He}}^{+}$ + He → ${\mathrm{He}}^{+}$ + He*, excitation at low incident ion energies (≲1 keV) proceeds via a pseudocrossing of the elastic ${}_{}{}^2{}_{}{}^{}\Sigma _g^{}{}_{}{}^{}$ diabatic potential with excited-state ${}_{}{}^2{}_{}{}^{}\Sigma _g^{}{}_{}{}^{}$ potentials. In addition, pseudocrossings of inelastic potentials at large internuclear separations mix the amplitudes of the excited-state channels coherently. This many-state mechanism provides qualitative understanding of diverse experimental observations.