A precession of the conduction-electron spin polarization $\overrightarrow{\mathrm{P}}$ away from the initial direction defined by the direction of the circularly polarized pumping light beam is found in photoemission experiments from GaAs(110)/(Cs,O). This precession occurs in the band-bending region about specific crystallographic directions and arises from the spin-orbit-induced spin splitting of the conduction band. These findings open new possibilities for the investigation of the electronic properties of this important interface region.

• Received 21 February 1984

DOI:https://doi.org/10.1103/PhysRevLett.52.2297