Strong velocity dependence of the atomic alignment effect inNa(3p)+Na(3p)associative ionization

We have directly measured the effect of $p$-orbital spatial alignment on the associative-ionization (AI) cross section in $\mathrm{Na}\mathrm{}\left(3p\right)+\mathrm{Na}\mathrm{}\left(3p\right)\mathrm{}$ collisions as a function of collision velocity in crossed atomic beams. Our measurements show that anisotropy in the cross section grows rapidly with velocity and that AI increasingly favors $p$-orbital alignment of both partners parallel to the laboratory collision axis over all other possible relative laboratory orientations.