Atomic shadows

You cannot see anything smaller than an atom with a visible light microscope, because anything smaller is shorter than the shortest wavelength. Australian scientists have pushed microscopy to the limits though by proving that it just takes one atom to cast a shadow. David Kielpinski of Griffith University, working with Erik Streed and their colleagues reveal details in a recent issue of Nature Communications of how they isolated a single atom of ytterbium in a vacuum and held it still long enough to get a snapshot. The work points the way to stretching the limits of light spectroscopy to complex biological molecules that are often damaged by ultraviolet or X-rays and so become less amenable to study at those more energetic wavelengths.