Claire Vallance
Professor Claire Vallance
Professor of Physical Chemistry
Our group works in the general areas of chemical reaction dynamics and new spectroscopic methods and applications. Our work ranges from fundamental studies of photon and electron-induced chemistry to the development of new types of chemical sensor and applications of spectroscopy in medicine. Projects include:
1. Photoinduced and electron-induced chemical reactions
Chemical reactions initiated by light or by collisions with electrons play an important role in atmospheric chemistry, astrochemistry, synthetic chemistry, and biology. Understanding the mechanisms of these reactions in detail offers new insight into a range of vital physical and chemical processes, ranging from the breaking of a single chemical bond all the way through to complex multistep processes occurring in biological systems.
We study photoinduced and electron-induced chemistry in the gas phase, using velocity-map imaging to record scattering distributions of reaction products and covariance-map imaging to investigate correlations between different products. The measured scattering distributions provide a ‘fingerprint’ for the process under study, and can be analysed in order to unpick details of the reaction mechanism.
Examples of photochemical systems we have studied recently include photolysis of neutral and ionic ethyl bromide and ethyl iodide, which play a role in the marine boundary layer of the Earth's atmosphere, and photolysis of N,N-dimethylformamide, a model for peptide bond fragmentation. We are currently studying electron-initiated processes relevant to radiation-induced damage to DNA and formation and destruction of polycyclic aromatic hydrocarbons (PAHs) in interstellar gas clouds.
2. Ultrafast detectors for time-of-flight imaging
We are part of the PImMS (Pixel Imaging Mass Spectrometry) consortium, a group of researchers working to develop ultrafast imaging sensors suitable for applications in time-of-flight mass spectrometry. The sensors allow velocity-map or spatial-map images to be acquired for each mass peak in a time-of-flight mass spectrum, opening up a range of new applications in mass spectrometry, state-of-the-art chemical dynamics studies, neutron detection, and other fields of science. More information on the PImMS detectors is available here: pimms.chem.ox.ac.uk.
3. Spectroscopic and mass spectrometric measurements in clinical medicine
We are working with clinicians and researchers in cardiology, vascular surgery, and neurosurgery at the John Radcliffe hospital to develop various types of spectroscopy for the analysis of clinical samples. Projects include: (i) evaluating whether reflectance spectra of thrombus removed from coronary arteries following STEMI (heart attack) can be used to classify patients into high and low risk groups, and therefore to guide clinical decisions during the acute treatment phase; (ii) investigating the use of Raman and fluorescence spectroscopy and mass spectrometry for the genetic characterisation of brain tumours and delineation of tumour borders; (iii) rapid mass spectrometric analysis of tissue from abdominal aortic aneurisms to identify clinically relevant biomarkers.
4. Optical microcavities for chemical sensing
Over the past few years we have been working with Prof. Jason Smith's group in Oxford Materials to develop miniature optical cavities for applications in solution-phase chemical sensing and nanoparticle characterisation. Microcavities are only a few wavelengths in length, giving them interesting optical properties, and contain tiny quantities of liquid, often only a few tens of femtolitres. As with any optical cavity, light forms standing waves known as cavity modes at well-defined frequencies within the cavities. By tracking changes in the frequencies and intensities of individual cavity modes when a sample is introduced into the cavity, we can detect and characterise single nanoparticles, and perform chemical sensing down to the few-molecule level. Most of this work has now been transferred into our new spin-out company, Oxford HighQ oxfordhighq.com, where it is being developed into nanoparticle characterisation instruments for nanomedicine research and industry and environmental sensors for water monitoring.
Claire Vallance is a Professor of Physical Chemistry at the University of Oxford, Tutorial Fellow in Physical Chemistry at Hertford College, and current President (until July 2021) of the Faraday Division of the Royal Society of Chemistry. She has research interests spanning chemical reaction dynamics, the development of laser spectroscopy techniques for chemical sensing, and the application of mass spectrometry and spectroscopy in clinical medicine. In addition to research publications, Claire has published the textbooks Astrochemistry: from the Big Bang to the Present Day, An Introduction to Chemical Kinetics, An Introduction to the Gas Phase, and a ChemLibre textbook on Symmetry and Group Theory, and co-edited Tutorials in Molecular Reaction Dynamics with colleague Mark Brouard. She is co-inventor of the PImMS ultrafast imaging camera (pimms.chem.ox.ac.uk), and in 2018 co-founded the spin-out company Oxford HighQ (oxfordhighq.com) with Jason Smith from Oxford Materials and postdocs Aurelien Trichet and Dean James. In 2020, Oxford HighQ was awarded a Business Start-up award from the Institute of Physics. Prior to her present appointment, Claire held a Royal Society University Research Fellowship and a Violette and Samuel Glasstone Fellowship, also at Oxford. She obtained her BSc (Hons) and PhD from the University of Canterbury in Christchurch, New Zealand, where she worked with Peter Harland on steric effects in collisions of spatially oriented molecules.
