Differential cross section for Na fine-structure transfer induced by Na and K collisions

The electronic energy-transfer process ${\mathrm{Na}}^{\mathrm{*}}$(3${\mathrm{P}}_{3/2}$)+M→${\mathrm{Na}}^{\mathrm{*}}$ (3$P_{1/2}$)+M, where M is an Na or K atom, has been measured differentially with respect to scattering angle. This has been done with crossed beams and by establishing the final (3$P_{1/2}$) state velocity distribution from the Doppler spectrum of 3$P_{1/2}$→4$D_{3/2}$ absorption. The differential cross section for Na perturbers is highly forward peaked (within a few degrees) with a small but extended high-angle tail. Forward angles are also dominant for K perturbers, but these cover a larger angular range with a very substantial large-angle contribution.