‘Watching’ atoms move on atomic length and time scales with helium spin echo

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• Dr John Ellis, Cavendish Laboratory
• Wednesday 17 October 2018, 20:00-21:00
• Wolfson Lecture Theatre, Department of Chemistry, Lensfield Road.

If you have a question about this talk, please contact Fionn Bishop.

A major scientific milestone was the advent in the early 1980’s of the ability to image individual atoms, but with it came the realisation that actually what we wanted was to be able to watch them move, yet direct imaging would require framing rates of many of THz – an apparently unattainable goal. In this talk the Helium ‘spin echo’ scattering technique is outlined which gives a direct handle on atomic motion at surfaces on the pico to nano second time scale, and enables us to ‘watch’ atoms move – albeit in reciprocal space and correlation time.

This experimental capability enables us to probe a wide range of atomic scale dynamical phenomena. Do you actually need quantum mechanics to model thermally activated motion? If you make a nano motor of a few molecules – what atomic scale friction can you expect? And then the fundamental question of how do you work out how fast a thermally activated process occurs – till now no one has been able to measure accurately enough to evaluate theoretical methods. The result of the test is quite telling: current theories are hopelessly inaccurate, yet their inadequacies were outlined in 1940. Why does no one take any notice? Everyone just soldiers on as though blindfolded…

This talk is part of the Cambridge University Physics Society series.

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