Electron resonances in DIET

The appearance of peaks or maxima in desorption yield functions, obtained by 5 to 20 eV electrons impinging from vacuum onto atomic or molecular solid films, reveals the formation of transient anions (i.e. electron resonances) at specific energies. Depending on the interaction of the incident electron with a particular atom or molecule and with the surrounding medium, the transient anion can cause desorption of a stable anion and one or more neutral fragments or only neutral particle ejection. The former process occurs when the transitory anionic state dissociates before autoionization, whereas decay by electron emission can, under certain circumstances, result in neutral atom or molecule desorption. Details on these mechanisms are given in this article. They are illustrated from desorption yield functions recorded for 5–20 eV electron impact on thin film targets made of pure Ar, CO2, D2O and mixtures of Ar with H2O, O2 and n-hexane.