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 begin from the assumption of statistically-averaged internal energy. This assumption 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.

Collisions between electrons and molecules underpin a wide variety of fundamental chemical processes. Despite their importance, electron-driven chemistry is still poorly understood..

In the NURD Lab, we are fundamentally concerned with inelastic collisions that lead to excitation or ionisation of the molecule.

Unlike photon-initiated chemistry, inelastic collisions between electrons and molecules don't obey the typical spectroscopic selection rules, and tends to lead to an ensemble of simultaneous product-states.

Some of the biggest challenges in this field are:

1) How should we treat the collision process and energy transfer in the collision?

2) What tools do we have at our disposal for treating the broad range of accessible states in energetic collisions.

3) How do we track multiple competing pathways simultaneously?

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.