  We report on a novel transport phenomenon realized by optical pumping in
surface state electrons on helium subjected to perpendicular magnetic fields.
The electron dynamics is governed by the photon-induced excitation and
scattering-mediated transitions between electric subbands. In a range of
magnetic fields, we observe vanishing longitudinal conductivity sigma_xx. Our
result suggests the existence of radiation-induced zero-resistance states in
the nondegenerate 2D electron system.
