On the dynamical description of K - K charge transfer in highly ionised ion - atom collision systems

We examine the role of electronic relaxation in the description of K-K charge transfer for ion-atom collisions with bare or one-electron projectiles in the intermediate velocity region. Total and differential K-K transfer cross sections for the system F9+ +Si are calculated within the coupled-state impact parameter method, starting from a relaxed molecular Hamiltonian and from a frozen two-centre Hamiltonian. By comparing the results of the two molecular expansion calculations with each other and with those of the atomic orbital expansion method, we test the various assumptions about relaxation of passive as well as active electron orbitals in a single-electron molecular orbital picture. A comparison with experimental data favours the description with relaxation in neither active nor passive orbitals for collision energies above 400 keV amu-l.