Chirita-Mihaila, M. C., Szabo, G., Redl, A., Goldberger, M., & Wilhelm, R. A. (2023, September 12). Ultrafast ions for time-resolved ion surface collision experiments [Conference Presentation]. 24th International Workshop on Inelastic Ion-Surface Collisions (IISC-24), Charleston, South Carolina, United States of America (the).
In contrast to electrons or photons, ion pulses are currently not available in the range of picoseconds or below. The main reason is the !arge initial momentum given by the ion mass, which limits the achievable timing precision of an ion impact on a surface or molecule (1,2].
We use a femtosecond laser system with UV light in order to trigger ultrafast electron emission from a photocathode in the linear emission regime. Optimizing for highest electron intensity per pulse, we propagate the electrons through a set of high-voltage electrostatic lenses and a strong axial magnetic field. Electron impact ionization of atoms and molecules in the gas phase leads to the formation of ions. Interestingly, due to overfocussing by the magnetic field, electrons can impact the positively- biased electrostatic Jens optics and trigger ultrafast electron-stimulated desorption (incl. ionization) which is seen by measuring short (< 200 ps) proton pulses independent of gas background pressure. In this case the initial momentum distribution of the molecular or atomic species to be ionized is not isotropic anymore breaking potentially the present pulse width barrier.
