Researchers Develop Technique to Generate Beams of Single Mass-Selected Charged Ice Particles

Scientists have developed a new technique to produce low-intensity beams of single mass-selected charged ice particles under vacuum. The research team, led by Anatolii Spesyvyi from the University of Cologne, used electrospray ionization (ESI) of water at atmospheric pressure to generate the particles. The particles underwent evaporative cooling when transferred to vacuum through an atmospheric vacuum interface.

The researchers achieved m/z selection, or selection based on the ratio of mass to charge, through two subsequent quadrupole mass filters operated in the variable-frequency mode. This allowed them to obtain accurate control over the particle masses. Velocity and charge of the selected particles were measured using a nondestructive single-pass image charge detector.

The apparatus allowed the preparation of beams of single particles with a repetition rate between 0.1 and 1 Hz, with various diameter distributions from 50 to 1000 nm at 30–250 eV of kinetic energy per charge. These distributions corresponded to velocities and particle masses quickly available between 600 m/s (80 nm) and 50 m/s (900 nm) and particle charge numbers (positive) between 103 and 104[e], depending on the size.

The development of this technique is significant because small ice particles play a role in atmospheric and extraterrestrial chemistry. In particular, circumplanetary ice particles that are encountered by space probes at hypervelocities play a critical role in determining the surface and subsurface properties of their source bodies.

The study demonstrated the correspondence between particle mass and specific quadrupole potentials in this device. This allows for the preparation of charged ice particle beams with selected narrow mass and kinetic energy distributions.

The apparatus is expected to be useful in further research in atmospheric and extraterrestrial chemistry, as well as in materials science and nanotechnology. It could also have applications in the field of space exploration, as the precise control over particle mass and kinetic energy could enable more accurate study of the properties of ice particles encountered by space probes.

Overall, the development of this technique represents a significant advancement in the field of mass spectrometry (MS) and is expected to have broad implications in a range of scientific disciplines.

Reference

(1) Spesyvyi, A.; Žabka, J.; Polášek, M.; Charvat, A.; Schmidt, J.; Postberg, F.; Abel, B. Charged Ice Particle Beams with Selected Narrow Mass and Kinetic Energy Distributions. J. Am. Soc. Mass Spectrom. 2023. DOI: 10.1021/jasms.2c00357