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upstart writes in with an IRC submission:

An experiment suggested by a Ph.D. student may rewrite chemistry textbooks:

The project looked at a fundamental question: Which properties are inherent to a metal and which are incidental?

[...] The scientists cooled ammonia—normally a gas at room temperature—to minus 33 C to liquify it and then added, in separate experiments, the alkali metals lithium, sodium and potassium.

In these solutions, electrons from the alkali metal initially become trapped in the gaps between ammonia molecules. This creates what scientists call 'solvated electrons,' which are highly reactive but stabilized in the ammonia. These solutions have a characteristic blue color. But given enough solvated electrons, the whole liquid turns bronze and, in essence, becomes a metal while remaining liquid.

[...] The scientists next measured the amount of energy needed to bump the solvated electrons out of metallic ammonia using an extremely bright and focused X-ray beam based in Berlin.

In a first-ever experiment, they forced different concentrations of the metallic ammonia through a microjet, which created a stream about the width of a human hair that then passed through a hair-thin X-ray beam.

The results showed that, at low concentrations, solvated electrons were more easily dislodged from the solution by the interaction with the X-rays, giving a simple energy pattern. At higher concentrations, though, the energy pattern suddenly developed a sharp band edge, indicating the solution was behaving as a metal would.

Journal Reference:
Tillmann Buttersack, Philip E. Mason, Ryan S. McMullen, et al. Photoelectron spectra of alkali metal–ammonia microjets: From blue electrolyte to bronze metal [$], Science (DOI: 10.1126/science.aaz7607)

Original Submission