Assessing electron emission induced by pulsed ion beams: A time-of-flight approach

We present a method to measure the kinetic energy of electrons emitted upon ion impact via their time-of-flight. Pulsed beams of H⁺, D₂⁺, He⁺ and Ne⁺ ions with velocities between 0.4 and 3.5 a.u. are transmitted through thin, self-supporting carbon and gold foils. Transmitted ions and secondary electrons are detected with a position-sensitive detector behind the sample, and their respective energies are determined via their flight times. A coincidence criterion can be applied in the acquisition software. Measured electron energies range between 10 and 400 eV. Above ion velocities of 1 a.u. the most probable electron energy scales with ion velocity pointing towards a kinetic emission mechanism. At lower ion velocities, the electron energy stays constant and lies above the maximum energy transfer possible in a classical binary collision between ion and electron. Potential applications and technical challenges of measuring electron energies and yields with a time-of-flight approach are discussed.