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Evidence for Superfluidity in Para-Hydrogen Clusters Inside Helium-4 Droplets at 0.15 Kelvin
1Max-Planck-Institut für Strömungsforschung, Bunsenstrabetae 10, 37073 Göttingen, Germany. General Physics Institute, Russian Academy of Sciences, 117942 Moscow, Russia.
Science (New York, N.Y.)
|September 1, 2000
Summary
This study used infrared spectroscopy to investigate molecules in helium droplets. Results suggest the first evidence of superfluidity in a liquid other than helium.
Area of Science:
- Quantum Fluids and Solids
- Spectroscopy
- Low-Temperature Physics
Background:
- Superfluidity is a quantum mechanical phenomenon observed in liquid helium.
- Understanding superfluidity in other systems can reveal fundamental physics.
- Helium droplets provide a unique environment for studying quantum phenomena.
Purpose of the Study:
- To investigate the behavior of carbonyl sulfide (OCS) molecules in helium-4 ((4)He) and mixed (4)He/(3)He droplets.
- To explore the excitation of angular momentum around the OCS axis in different helium environments.
- To provide evidence for superfluidity in a liquid beyond helium.
Main Methods:
- Infrared spectroscopy was employed to analyze OCS molecules doped with para-hydrogen (pH(2)) or ortho-deuterium (oD(2)).
- Experiments were conducted in pure (4)He droplets at 0.38 K and mixed (4)He/(3)He droplets at 0.15 K.
- Spectral features related to angular momentum excitation were monitored.
Main Results:
- In pure (4)He droplets, spectral features indicated excited angular momentum for both pH(2) and oD(2).
- In colder mixed (4)He/(3)He droplets, these features persisted for oD(2) but disappeared for pH(2).
- The disappearance of spectral features in pH(2) suggests the cessation of angular momentum excitation.
Conclusions:
- The observed changes in spectral features are consistent with the onset of superfluidity in the mixed droplets.
- This study presents the first spectroscopic evidence for superfluidity in a liquid system other than helium.
- The findings open new avenues for exploring quantum phenomena in novel superfluid environments.
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