Making molecular movies

Researchers from the Centre of Excellence for Coherent X-ray Science in the Department of Physics at the University of Melbourne have found a new way of imaging the nanoworld, using electrons (as with an electron microscope) but at higher resolution and higher speeds.

Electron microscopy has revolutionised science by showing us the structure of things at micron and even nanometre scales. But electron microscopy is far too slow to capture critical dynamic processes, such as the folding of a protein molecule, which requires time resolution in the picosecond (billionth of a billionth of a second).

This work takes an important step towards producing atomic resolution images on atomically relevant timescales. The researchers have shown that electron bunches generated from laser-cooled atoms can be both very cold and ultrafast.

The temperature of the electrons determines how sharp the images can be and the pulse duration sets the timescale on which dynamics can be observed.

A common analogy for this imaging is that it is a bit like making a ‘molecular movie’ say the researchers. The temperature of the electrons is akin to the quality of lighting and the camera used and determines how sharp the images can be; while the electron pulse duration has a similar effect to shutter speed. Good movies of fast action require both cold and fast electrons.

The team has been able to combine these two qualities, generating ultrafast electron pulses with cold electrons, paving the way for ultrafast high-resolution electron imaging.

Ultimately, this unique combination of techniques has the potential to realise the brightness and coherence requirements for single-shot electron diffraction from crystalline biological samples, which has applications in solid-state physics and rational drug design.

The work published this week in Nature Communications.