X-ray probing of controlled photo-induced dynamics

Lead Research Organisation: Imperial College London
Department Name: Physics


The quantum control of photo-induced dynamics in matter is a scientifically challenging and technology important objective. Given the key role conical intersections (multi-dimensional potential surface crossings) are now believed to play in photochemistry it is especially intriguing to consider the possibility to steer the quantum path of an evolving molecular system across a conical intersection. This may be done by preparing a coherent superposition of electronic states and steering the evolution of this superposition during the crossing. Given the ultrafast nature of the dynamics normally associated with the crossing of a conical intersection and the large coherent bandwidth required to prepare an electronic state superposition, which itself requires a very short (few femtosecond) light pulse we must have laser fields operating at extremely short timescales to achieve this. Further we require a probing method with sufficient time resolution and electronic state specificity to track and confirm the dynamics and their control.
The project will use our high harmonic generation based X-ray method - shown to be capable of generating sub-femtosecond X-ray pulses from 100 eV to 600 eV to probe gas phase photochemical reactions- to probe the dynamics through time resolved near edge spectroscopy at C and N K edges. This photochemistry will in turn be triggered via deep UV pulses generated using non-linear optical methods (e.g. photonic crystal fibre generate dispersive waves) and controlled using a few-cycle laser pulses synchronously generated with the pump and probe. The work will pioneer new techniques in the ultrafast laser technology required for probing dynamics in matter at extreme timescales.


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