Probing the presence and absence of metal-fullerene electron transfer reactions in helium nanodroplets by deflection measurements.

Metal-fullerene compounds are characterized by significant electron transfer to the fullerene cage, giving rise to an electric dipole moment. We use the method of electrostatic beam deflection to verify whether such reactions take place within superfluid helium nanodroplets between an embedded C molecule and either alkali (heliophobic) or rare-earth (heliophilic) atoms. The two cases lead to distinctly different outcomes: CNa ( = 1-4) display no discernable dipole moment, while CYb is strongly polar.