Sunday, January 29, 2023

What is the smallest thing ever photographed?

It is the shadow produced by… an atom.

A team of researchers from Griffith University in Queensland (Australia) wanted to understand how many atoms were needed to generate a shadow and realized, with considerable surprise, that only one was enough.

The researchers had to wait five years for the atom to freeze and for its shadow to become dark enough to be visible.

In detail, David Kielpinski and colleagues confined atomic ions of ytterbium, a soft silvery metal (whose atomic number is 70), in a trap kept under high vacuum and at a temperature of a few millikelvins.

Next, a single ion was struck by light of a specific frequency and cast its shadow on a detector.

Only then was the digital camera connected to a very high resolution electron microscope able to capture the image you see in the figure.

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