Non-linear phenomena in mobility of two-dimensional electron system on the liquid helium surface

The dependence of the mobility on driving electric field for electrons localized in two-dimensional electron layer on the liquid helium surface has been studied at temperatures below 1 K in the region of electron-ripplon scattering. The measurements are carried out at electron concentrations lower than those leading to screening the holding electric field by the field of electron layer (unsaturated case). The character of the dependence of mobility on driving field is shown to be a result of determining contribution of two-ripplon mechanism of energy relaxation in surface electron system under its overheating. The data obtained agree with theoretical dependences obtained under the supposition of coinciding the short-wave region of ripplon spectrum with long-wave asymptotics