Group aims and focus

Predicting or rationalising how a molecule fragments upon ionisation in a mass spectrometer is an ongoing issue for analytical chemistry. A molecules fragmentation pattern can be considered a fingerprint of its structure, and thus understanding how reactants become products is of critical importance. Most models to predict fragmentation patterns rely on statistical theories such as Rice-Ramspberger-Kessel-Marcus, otherwise known as RRKM theory and quasi-equilibrium theory to deduce reaction mechanisms. This method, which assumes that internal energy of the ion is evenly distributed amongst all available degrees of freedom (vibration, rotation, electronic), fails to capture the chemistry that outcompetes IVR, so-called non-ergodic dynamics.

In the NURD lab, we use femtosecond strong-field ionisation to generate highly-excited molecular cations and then used time-resolved mass spectrometry to probe their rearrangement and dissociation into products in real-time. We are also interested in utilising diffractive imaging methods such as ultrafast electron diffraction and/or X-ray scattering to image the ultrafast structural dynamics of molecular cations.

Photochemistry and photochemical dynamics is a mature field of research, but only represents a small fraction of chemical science.

Electron collision-initiated chemistry is perhaps even more fundamental, but is far less well understood, particularly on the ultrafast timescale.

Our group is developing new tools and adapting existing tools from photochemistry to understand electron-initiated chemistry on an ultrafast timescale.

To understand the transition-state of a chemical reaction is to understand the fundamental link between reactants and products. However, the transition-state is an ephemeral concept that can only be inferred from experimental results and theoretical models. Molecular Movies are an attempt to discard inference, and look directly at chemistry in motion. A Molecular Movie is almost exactly what it sounds like, a series of images that when combined, show a molecule in motion.

Making a Molecular Movie is also about as challenging as it sounds. There are several approaches to doing this, which rely on many overlapping sets of experitise. So we collaborate! Our group will periodically join forces with other groups from around the world to visit state-of-the-art research facilities called X-ray Free Electron Lasers (XFEL) and use advanced charged-particle and/or diffractive imaging techniques to try to capture electronic and nuclear dynamics in real-time.