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1. Femtosecond Transient Absorption Spectroscopy

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   Femtosecond Transient Absorption Spectroscopy (femtosecond transient absorption spectroscopy (FTAS)/)) is a sophisticated pump-probe technique used to monitor the ultrafast dynamics of excited electronic states in matter, typically ranging from femtoseconds ($10^{-15}$ s) to several nanoseconds ($10^{-9}$ s). The core principle relies on exciting a sample with an intense, ultrashort 'pump' pulse and subsequently probing the resulting changes in absorption cross-section using a time-delayed, lower-intensity 'probe' pulse. The time…