Low energy electron beam for time-of-flight ionization measurements

A low energy electron gun was assembled in a crossed molecular beam apparatus in order to monitorize the effusive molecular beam density using the electron impact technique. Electrons were analised in both time-of-flight and Faraday cup detectors. The electrons coming directly from the gun were clearly identified, allowing those ones coming from the ionization impact to be distinguished in time-of-flight with a multichannel analyser working in PHA mode. This set-up allows to make an estimation of the electron impact cross-section ratios in CCl4 and air.