3 research outputs found
Laser-induced forced evaporative cooling of molecular anions below 4 Kelvin
The study of cold and controlled molecular ions is pivotal for fundamental
research in modern physics and chemistry. Investigations into cooling molecular
anions, in particular, have proven to be of key consequence for the production
of cold antihydrogen, the creation, and study of anionic Coulomb crystals as
well as in atmospheric research and astrochemistry. The commonly used anion
cooling technique via collisions with a buffer gas is limited by the
temperature of the used cryogenic cooling medium. Here, we demonstrate forced
evaporative cooling of anions via a laser beam with photon energies far above
the photodetachment threshold of the anion. We reach runaway evaporative
cooling of an anionic OH ensemble from an initial temperature of 370(12)
K down to 2.2(8) K. This corresponds to three orders of magnitude increase in
the ions' phase space density approaching the near-strong Coulomb coupling
regime. A quantitative analysis of the experimental results, via a full
thermodynamic model including the role of intrinsic collisional heating,
represents the anion cooling dynamics without any fitting parameters. This
technique can be used to cool, in principle, any anionic species below liquid
helium temperature, providing a novel tool to push the frontiers of anion
cooling to much lower than the state-of-the-art temperature regimes