The spin polarization of photoelectrons emitted by an activated gallium arsenide photocathode excited with circularly polarized light has been measured by an optical method: A crossed-beam experiment has been performed in which polarized electrons transfer spin angular momentum to zinc atoms in inelastic exchange collisions. The polarized atoms emit circularly polarized light in the direction of the spin transfer. The degree of circular polarization is directly related to the electron polarization.

• Received 19 June 1980

DOI:https://doi.org/10.1103/PhysRevLett.45.1171