At a collision energy E=0.1 eV we see a large polarization effect ${\mathit{Q}}_{\mathrm{ion}}^{\mathrm{*}{\mathit{M}}_{\mathit{j}}\mathrm{*}=0,1\mathrm{}}$/${\mathit{Q}}_{\mathrm{ion}}^{{\mathit{M}}_{\mathit{j}}\mathrm{*}=3\mathrm{}}$=2.5, decreasing to 1.4 for E≥1 eV. A two-state basis is used for the autoionization width of the π and σ orientations of the (2p${)}^{\mathrm{-}1}$ core hole, resulting in a preference for the Ω=0,1 molecular states as seen at 0.1 eV. The energy dependence is due to the decrease of ‘‘locking’’ of J to the internuclear axis with increasing angular velocity φ̇, leading to the semiclassical criterion ${\omega }_{\mathrm{prec}=4\mathrm{}\mathrm{\phi }\mathrm{̇}}$ for the transition from a space-fixed to a body-fixed description of J.

• Received 7 March 1989

DOI:https://doi.org/10.1103/PhysRevLett.62.2369