UltraFAST PhotoCHEMistry Induced by Light – ‘FASTCHEM’

Transient absorption spectroscopy (TAS) is a widely used spectroscopic technique based on detecting photoinduced absorption changes in a sample. If the excitation and detection light sources used in TAS have femtosecond (i.e. one millionth of one billionth of a second) time resolution, then we have a viewing glass into the fundamental processes in operation immediately after the molecule, or material, absorbs light. This is incredibly powerful as molecular transformations triggered by absorption of light occur on the timescale of molecular vibrations which typically happen on tens to hundreds of femtosecond (fs) timescales. The ability to observe these ‘ultrafast’ dynamics and assess how they are influenced by structural changes is formidable as the extra dimension of dynamics, allows us to transform the structure-function approach to molecule and material design to a more complete structure-dynamics-function approach, allowing us to enhance the performance of materials in photomedicine, photostability, photocatalysis, and photonics.
At the heart of the UltraFAST PhotoCHEMistry Induced by Light – ‘FASTCHEM’ – facility is a bespoke fs-TAS instrument that, in addition to having fs-TAS capabilities, has transient reflection and fluorescence up-conversion capabilities meaning we can investigate materials that are also poorly transmissive – TAS requires light to transmit through sample – and weakly light emissive (e.g., photocatalyst mounted on a non-transparent medium). Combined, these capabilities span the time-window of femtoseconds to milliseconds, with spectral coverage from ultraviolet to near-infrared. The result is an instrument that tracks photoinduced dynamics in exceptional detail; the kind of detail that is essential if one is seeking to fine tune the performance of photoresponsive materials. There is also a custom-built variable sample mounting arrangement, enabling both the more traditional vertical setup and new horizontal setup. This enables potential...