Polarization and Interference Effects in Ionization of Li by Ion Impact

We present initial-state selective fully differential cross sections for ionization of lithium by 24 MeV ${\mathrm{O}}^{8+}$ impact. The data for ionization from the $2s$ and $2p$ states look qualitatively different from each other and from $1s$ ionization of He. For ionization from the $2p$ state, to which in our study the $m_L=-1$ substate predominantly contributes, we observe orientational dichroism and for $2s$ ionization pronounced interference which we trace back to the nodal structure of the initial-state wave function.

Figure 1

Three-dimensional, fully differential angular distributions of electrons ejected from the (a) $2p$ and (b) $2s$ state of Li by 24 MeV ${\mathrm{O}}^{8+}$ impact. The electron energy is fixed at 1.5 eV and $q$ at 0.3 a.u. for the $2p$ state and at 1.0 a.u. for the $2s$ state.

Figure 2

Cut through the azimuthal plane of the FDCS shown in Fig. 1 for the $2p$ (open red symbols) and $2s$ states (solid blue symbols). Dashed curves, CDW-EIS calculations; solid curve, CDW-EIS-NN calculations. For explanation of theoretical models, see text.