Generation and Control of Picosecond Ion Pulses via Laser-Stimulated Desorption from a Tungsten Nanotip

Abstract

We present a novel approach for generating and manipulating ultrashort ion pulses with durations of less than 100 ps, using a compact laser-stimulated desorption ion source. The setup utilizes an electrochemically etched tungsten nanotip with 150 nm apex radius, which is biased at high voltage and irradiated with femtosecond ultraviolet (259 nm) laser pulses. Surface- adsorbed species are ionized and desorbed from the tip, producing keV-energy ion pulses that are intrinsically synchronized with the laser. We systematically explore the dependence of ion pulse width and yield on laser pulse energy, repetition rate, polarization, working gas species, and extraction voltages. Time-of-flight (TOF) spectroscopy reveals tunable picosecond ion pulses for various adsorbate-capable species, including hydrogen, deuterium, nitrogen (shown in Figure 1). The source operates at moderate optical fluence (~1011 W/cm2) and achieves a full width at half maximum (FWHM) of 84 ps for hydrogen ions.