We report the measurement of state-to-state differential cross sections for rotationally inelastic electron-${\mathrm{Na}}_2$ collisions for impact energies from 150 to 300 eV. The data demonstrate for the first time large rotational transitions (0≤Δj≤30) for backward scattering. The most surprising result is the observation of pronounced rotational rainbows. These structures are expected to be general features in high-energy electron-molecule scattering.

• Received 18 March 1987

DOI:https://doi.org/10.1103/PhysRevLett.58.2642