Very short fluorescence lifetimes evidence ultrafast deactivation of photoexcited molecules. To unveil the underlying mechanism for two compounds exhibiting (sub)picosecond emission dynamics, we combine femtosecond fluorescence upconversion with high-pressure liquid-phase spectroscopy. For the triazene berenil, the absence of a pressure dependence corroborates a bicycle-pedal motion as deactivating process. In the thiacyanine NK88 which may undergo a bi-phasic deactivation, our results suggest that kilobar pressures lead to a modification of the excited-state potential energy surface, thereby changing the branching ratio of two competing pathways and opening a possibility to steer the product distribution of the photoreaction.
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