Professor Fielding is recognized internationally for her original work in the field of spectroscopy and dynamics of excited state of molecules. Her work has been truly innovative. During the last 10 years, she has designed and built four separate experiments employing photoelectron spectroscopy to study small neutral molecules in the gas-phase, large molecular anions in the gas-phase, molecules on surfaces and organic chromophores in aqueous solution and in proteins. She has developed collaborations with synthetic organic chemists to create molecules with specific molecular and electronic structures. She has developed expertise in electronic structure theory to support the interpretation of her experimental work and maintains a long-standing collaboration with Professor Graham Worth at UCL who carries out complementary high-level electronic structure calculations and dynamics calculations.
Highlights of her research studying neutral molecules in the gas-phase include the discovery that ultrafast intersystem crossing competes with internal conversion in the prototypical organic molecule benzene and unravelling the role of the 3s Rydberg component of dissociative states in the non-radiative decay of hetero-aromatic molecules. Recently, she discovered an entirely new non-radiative decay pathway in pyrrole dimers and believes that this low-energy, photo-induced electron-transfer process is likely to play a key role in the electronic relaxation of biological and technological systems containing the pyrrole building block and other heteroaromatic molecular motifs.
During the last 6 years, Helen has been a pioneer in the development of anion photoelectron spectroscopy as a tool for unravelling the electronic structure and dynamics of photoactive protein chromophores. Highlights include showing that the first electronically excited state of the isolated green fluorescent protein chromophore anion in the gas-phase is bound with respect to electron detachment, contradicting earlier theoretical predictions, finding that the relaxation dynamics in the gas-phase are identical to those in solution and demonstrating that the redox properties of the chromophore can be controlled by moving the position of a hydroxy group on the chromophore or chemical substituents with electron withdrawing or electron donating character.
Her current research interests include developing these techniques further to study larger molecular systems, to probe photochemistry and photobiology in the solution phase, and to using light to control photochemistry.