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Laser Group publish in Nature Chemistry

Press release issued: 4 October 2016

The translational, rotational and vibrational relaxation dynamics of a solute molecule

A paper by Bristol chemists to be published in Nature Chemistry reports unprecedented observations of how a hot molecule cools in a liquid solvent.  The experimental study was carried out by Michael Grubb, Philip Coulter and Hugo Marroux, working with Prof Mike Ashfold and Prof Andrew Orr-Ewing. The Bristol group’s ultrafast laser system provided snapshots of the cooling with time resolution of 10-13s (0.0000000000001 s or 100 femtoseconds).  Diatomic CN radicals were generated with high amounts of translational and rotational energy by ultraviolet laser photodissociation of BrCN dissolved in a liquid perfluorocarbon, and the time resolution of the experiments was high enough even to observe the Br-C bond breaking.   Subsequent measurements at increasing time delays after the bond dissociation revealed the way collisions with the solvent molecules reduced the speed and rotational motion of the CN radicals until they equilibrated with the temperature of the surrounding solvent. Computer simulations by Balázs Hornung successfully reproduced many features of the experimental observations.  

This study marks the most detailed exploration to date of how energy flows from a hot molecule into a surrounding liquid, and provides fresh insights into the extraordinarily complex behaviour of liquids.

Further information

The translational, rotational and vibrational relaxation dynamics of a solute molecule, M.P. Grubb, P.M. Coulter, H.J.B. Marroux, B. Hornung, R.S. McMullin, A.J. Orr-Ewing and M.N.R. Ashfold, Nature Chem. in press (2016). DOI: 10.1038/NCHEM.2570.

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