Strong Alignment Effect in Quasiresonant Charge Transfer between Laser-Excited Sodium Atoms andC60

We observe a strong alignment effect $(〈{\rho }_{\sigma \sigma }〉=0.8\mathrm{}\pm 0.2)$ in quasiresonant charge transfer collisions between $\mathrm{Na}\left(3p\right)$ and ${\mathrm{C}}_{60}$ at thermal energies. This implies that practically only excited sodium atoms with their electronic charge cloud asymptotically aligned along the relative velocity vector lead to charge transfer. This is interpreted as being due to a combination of “orbital locking” and the strong $\pi$-like character of the fullerene lowest unoccupied molecular orbital.