Trapping Electrons in Electrostatic Traps over the Surface of 4He

We have observed trapping of electrons in an electrostatic trap formed over the surface of liquid ⁴He. These electrons are detected by a Single Electron Transistor located at the center of the trap. We can trap any desired number of electrons between 1 and ∼30. By repeatedly (∼10³–10⁴ times) putting a single electron into the trap and lowering the electrostatic barrier of the trap, we can measure the effective temperature of the electron and the time of its thermalisation after heating up by incoherent radiation. E. Rousseau’s present address: Ecole Centrale, Paris, France. D. Ponarine’s present address: Chemistry Dept., North Carolina State Univ., Raleigh, NC 27695, USA.