Spying on Ultrafast Structural Changes Through Three Sets of Eyes

Modern ultrafast laser technologies have initiated a 'femtosecond revolution' revolution in chemical physics, allowing the motion of nuclei within molecules to be visualised on the femtosecond (millionth of a billionth of a second) timescale. The insights from femtochemistry experiments allow detailed probing of the mechanics underpinning chemical reactions, and are therefore invaluable for fundamental investigations into molecular structure and reactivity. This proposal aims to advance understanding of how carbonyls, a key class of organic molecules found within the earth’s atmosphere (with important implications for understanding radiative forcing and climate change), react upon excitation by ultraviolet light, using state-of-the-art ultrafast experimental techniques. Whilst this crucial photochemistry has been studied by other techniques previously, a deep understanding of the complex electronic and nuclear dynamics which control the outcomes of the possible photoreactions is, so far, elusive. Throughout the grant, three different experimental techniques (ultrafast electron diffraction, ultrafast X-ray diffraction and Coulomb explosion imaging), each offering complementary structural information, will be exploited to gain an exquisitely detailed view of this important fundamental photochemistry. By studying a series of related carbonyl molecules, insights will be gained into the broad class of carbonyl molecules as a whole. Furthermore, the results will also assess the relative applicability of these experimental techniques (which have only been facilitated by recent technological advancements in the field of free-electron laser science) to probing complex molecular photochemistry on the shortest timescales. Consequently, the results will be of wide-reaching impact both in the fields of atmospheric science and within the ever-growing multi-disciplinary community which utilizes modern free-electron lasers to record so-called 'molecular movies'.