The mobility of electrons on a liquid helium surface

The effective temperature approximation has been improved. We have calculated the averaged collision time of electrons on a liquid He-4 surface by means of the Gauss-Laguerre integration, where the interactions for the electron-ripplon and the electron-He vapor are considered as dominant scattering mechanisms. The results show that electrons stay mainly in the ground subband of the hydrogenic series when the drift field F-D less than or equal to 0.8 V/cm. Also the temperature ranges for which one of the above scattering mechanisms can be ignored have been discussed in detail.