Preparation of Molecular States in an Ion-Atom Crossed-Beam Scattering Experiment by Laser Excitation

In ${\mathrm{Na}}^{+}$-${\mathrm{Na}}^{*}$ scattering in the energy range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=25-50\mathrm{}$ eV the molecular states $\sigma$, ${\pi }^{+}$, and ${\pi }^{-}$ of the resulting ionic quasimolecule ${\mathrm{Na}}_2^{+}$ are prepared by laser-optical pumping of the sodium atom to the $3{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$, $F=3\mathrm{}$ state. Selection is made with linearly or circularly polarized light. With this novel approach, one can discuss the transition from the space-fixed to the body-fixed reference frame in detail. There is clear evidence for conservation of reflection symmetry with respect to the scattering plane and the implications are considered.