No abstract

Abstract. Using electric-field anticrossing techniques, we investigated the coherent excitation of n = 5-8 He I states with different orbital angular momenta by proton impact. These measurements give strong evidence that saddle dynamics of Hf-tike systems are well suited for describing the final phase of 12.5 keV H+-He collisions. We conclude that, besides electron promotion via the 2po-orbital, the collision system undergoes diabatic l sa-3da transitions during the close encounter and present an explanation of the electric dipole moments measured for excitation of H(n=2) states by H+-He and H-He collisions.