Abstract
The reaction pathway in the photoexcited model compound 2-methyl-5-phenylthiophene has been unravelled by Femtosecond Stimulated Raman Scattering and quantum chemical calculations. The excited state dynamics, including structural rearrangement, vibrational cooling and intersystem-crossing, will be presented.
Highlights
Background and significanceThere is continuing interest in the photo-physical properties of conjugated organic polymers, as there are significant processing advantages for using these materials to manufacture organic optoelectronic devices, such as photochromic molecular switches, solar energy conversion devices and light-emitting diodes
The performance of such materials depends on the fundamental properties of the constituent molecules, the dynamics of large polymeric systems are often difficult to discern due to structural heterogeneities
The system is subsequently interrogated by a pair of overlapped pulses: the joint presence of a broadband ultrashort probe pulse (PP) and a narrowband picosecond Raman pulse (RP) induces vibrational coherences which are read out as heterodyne coherent Raman signals free of fluorescence background, with simultaneous high spectral resolution and time precision [2]
Summary
There is continuing interest in the photo-physical properties of conjugated organic polymers, as there are significant processing advantages for using these materials to manufacture organic optoelectronic devices, such as photochromic molecular switches, solar energy conversion devices and light-emitting diodes. Ultrafast geometrical rearrangement affects the initial stages of charge separation and recombination and provides valuable clues about the chargetransport material properties. In this respect, spontaneous Raman (SR) represents a powerful tool to probe the geometrical configuration of molecular and solid-state systems. Taking advantage of its inherent sensitivity to the vibrational properties, it allows to extract structural and dynamical information. When it is used as a probe in time-resolved experiments to address transient phases, it has a critical shortcoming.
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