Amazing stuff!
"An international team led by chemists ... has reported strong experimental evidence for a superfluid phase in molecular hydrogen at 0.4 K.
This phase, theoretically predicted in 1972, had only been observed in helium and ultracold atomic gases until now, and never in molecules. The work could give scientists a better understanding of quantum phase transitions and collective phenomena. More speculatively, it could advance the field of hydrogen storage and transportation. ...
Previously, superfluidity had been observed in helium (3He and 4He) and in clusters of ultracold atoms known as Bose-Einstein condensates. In principle, molecular hydrogen (H2), which is the simplest and lightest of all molecules, should also become superfluid at ultracold temperatures. Like 4He, H2 is a boson, so it is theoretically capable of condensing into a superfluid phase. The problem is that it is only predicted to enter this superfluid state at a temperature between 1 and 2 K, which is lower than its freezing point of 13.8 K. ...
To keep their molecular hydrogen liquid below its freezing point ... confined small clusters of hydrogen molecules inside helium nanodroplets at 0.4 K. They then embedded a methane molecule in the hydrogen cluster and observed its rotation with laser spectroscopy. ..."
From the abstract:
"Molecular hydrogen (H2) has long been predicted to exhibit superfluidity—a state of zero viscosity—at extremely low temperatures. However, its existence remains under debate despite several experimental reports.
In this study, we investigated the infrared transitions of methane embedded in clusters of parahydrogen molecules at 0.4 K using high-resolution helium nanodroplet spectroscopy.
Our results revealed fully quantized rotational states of methane with minimal interference from surrounding H2 molecules, enabling precise determination of the rotational constant for each hydrogen cluster. The cluster-size dependence of the determined rotational constant aligns with behavior predicted by path-integral Monte Carlo simulations, indicating that more than 60% of the hydrogen molecules in the clusters participate in quantum bosonic exchanges, a characteristic feature of superfluidity.
This work provides strong experimental evidence for the existence of a superfluid phase of molecular hydrogen at 0.4 K, representing a major step forward in understanding quantum behaviors in molecular systems."
Hydrogen Molecule Becomes Superfluid: A 50-Year-Old Prediction Confirmed (original news release)
Exploring molecular superfluidity in hydrogen clusters (open access)
Experimental apparatus and laser used by researchers at the University of British Columbia, RIKEN and Kanazawa University to demonstrate superfluidity in hydrogen
No comments:
Post a Comment