  A spin-dependent emission of optically oriented electrons from p-GaAs(Cs,O)
into vacuum was experimentally observed in a magnetic field normal to the
surface. This phenomenon is explained within the model which takes into account
the jump in the electron g factor at the semiconductor-vacuum interface. Due to
this jump, the effective electron affinity on the semiconductor surface depends
on the mutual direction of optically oriented electron spins and the magnetic
field, resulting in the spin-dependent photoemission. It is demonstrated that
the observed effect can be used for the determination of spin diffusion length
in semiconductors.
