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takyon writes:

Physicists have observed relatively stable "macrodimers" made from two cesium atoms and used their predictive model to refine the binding energy and distance required to create macrodimers:

Experiments confirm the existence of 1-micrometer-sized molecules made of two cesium atoms by showing that their binding energies agree with predictions. Strongly bound diatomic molecules such as H₂ or O₂ are less than a nanometer across. Surprisingly, scientists have been able to create two-atom molecules more than a thousand times larger by using exotic atoms that attract one another only very weakly. Now, a pair of physicists have calculated what makes these "macrodimers" stable, and they have verified their predictions by creating micrometer-sized molecules containing two cesium atoms. The macrodimers could have applications in quantum computing.

Interest in these macromolecules stems from the challenges they pose to conventional understanding of molecules and bonds. More than a decade ago, physicists predicted that molecules with interatomic distances as large as 1 micrometer might be created by using a pair of atoms in so-called Rydberg states. These are atoms in which a single outer-shell electron has been excited to a high quantum state so that it orbits far away from the nucleus. Although Rydberg atoms are unstable, they can live as long as tens of microseconds, and experimenters have succeeded in creating macrodimers from them, confirming their existence indirectly by destroying them and detecting specific spectroscopic signatures.

However, physicists Heiner Saßmannshausen and Johannes Deiglmayr of the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, say that the earlier theoretical argument for the existence of macrodimers included some significant assumptions. To examine the argument more rigorously, they developed a sophisticated model of the interaction of Rydberg atoms and used it to predict in more detail the properties of stable macrodimers, such as the amount of energy binding them together. They then tested their model by creating the predicted molecules.

Observation of Rydberg-Atom Macrodimers: Micrometer-Sized Diatomic Molecules (DOI: 10.1103/PhysRevLett.117.083401) (DX)

Original Submission