Ion trap enables one minute in the nanocos­mos

The storage of helium nanodroplets in an ion trap enables a detailed investigation of the processes inside the droplets. The picture shows Matthias Veternik, PhD student and first author of the study, with the experimental setup.
Photo Credit: Universität Innsbruck

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Researchers successfully stored electrically charged helium nanodroplets in an ion trap for durations up to one minute, creating stable conditions similar to those found in space.
• Methodology: The team utilized a specialized ion trap device to capture and hold the nanodroplets, replacing previous methods that restricted observation to the brief flight time between the droplet source and a detector.
• Key Data: This new storage capability extends the experimental time window by a factor of 10,000 compared to prior millisecond-scale limits.
• Significance: The extended observation time allows for high-precision spectroscopic analyses of interstellar particle simulations and the identification of lifetime-limiting factors, such as collisions with residual gas or infrared-absorbing water molecules.
• Future Application: Upcoming developments involve incorporating detection cylinders to measure the mass-to-charge ratio of individual droplets, facilitating new forms of nanocalorimetry and time-resolved studies of chemical reactions.
• Branch of Science: Ion Physics and Applied Physics.

The new experiment allows helium droplets to be captured and stored for several seconds, opening up new possibilities for time-resolved investigations.
Graphical Abstract / et al: Physical Review Letters

At the Department of Ion Physics and Applied Physics at the University of Innsbruck, a research team has succeeded for the first time in storing electrically charged helium nanodroplets in an ion trap for up to one minute. This extends the time window for experiments with these extremely cold "mini-laboratories" by a factor of 10,000 compared to previous methods - and opens new possibilities for basic research in physics and chemistry. 

Helium nanodroplets are ultracold clusters consisting of helium atoms that come very close to the conditions that prevail for atoms and molecules in space. Among other things, this allows spectroscopic analyses of particles that occur in the interstellar medium to be carried out directly in the laboratory. Until now, however, the reaction and observation time was extremely short - investigations were generally limited to the flight distance between the droplet source and a detector, which is travelled in a few milliseconds. 

"The long storage time now enables detailed investigations of processes inside the droplets," explains Matthias Veternik, PhD student and first author of the study. "Initial analyses show that collisions with the residual gas in the vacuum chamber as well as infrared-absorbing molecules and clusters in the helium - such as water molecules - limit the lifetime of the droplets. This understanding is crucial in order to further optimize the trap technology." The investigations were supported by Prof Lutz Schweikhard from the University of Greifswald, who played a key role in the development of the new device with his many years of experience in the construction and application of ion traps. 

The new experiment allows helium droplets to be captured and stored for several seconds, opening new possibilities for time-resolved investigations. 

The new setup will allow chemical reactions and spectroscopic properties of molecules in ultracold helium droplets to be analyzed much more precisely and over longer periods of time. The next development step is already planned: "By incorporating detection cylinders into the ion trap, we can measure the passing, highly charged helium droplets using an induced signal and thus determine both the mass-to-charge ratio and the charge of each individual helium nanodroplet," explains Elisabeth Gruber, who was recently honored with an FWF-ASTRA Award to further develop this technology. "We want to use it to gain insights into the temporal development of charged helium droplets for the first time and develop a new form of nanocalorimetry." 

The results were recently published in the journal Physical Review Letters and emphasize the great potential of helium nanodroplets as an ultracold laboratory environment for future research. 

Published in journal: Physical Review Letters

Title: Extending the Observation Time of Charged Helium Droplets to the Minute Timescale

Authors: Matthias Veternik, Tobias Waldhütter, Lutz Schweikhard, Paul Scheier, and Elisabeth Gruber

Source/Credit: University of Innsbruck

Reference Number: phy012026_01

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