Generation of picosecond ion pulses using laser-stimulated desorption from a tungsten nanotip

Abstract

We present an experimental approach to the formation of sub-100 ps ion pulses at 4.5−8.5 keV energies using laser-stimulated desorption from a tungsten nanotip at room temperature. The illumination of the tip apex with femtosecond ultraviolet laser pulses results in the ionization of adsorbed atomic and molecular species through the enhancement of a localized electric field. Unlike photoionization of atoms and molecules in the gas phase in extended volumes, determined by a typical laser focal volume, our approach naturally exploits a nanometric ionization region from tungsten nanotips with tip radii of 15−150 nm and operates at a moderate optical fluence of 10¹¹ W/cm². Time-of-flight measurements demonstrate stable and well-timed ion pulses. A systematic exploration of the ion pulse characteristics on laser parameters and loading gas pressures has been conducted. Our compact, yet simple, source design renders time-resolved ion-solid interaction studies practically possible, paving the way for future pump-probe studies.