Photophysical and photochemical applications of femtosecond time-resolved transient absorption spectroscopy

The aim of this paper is to provide the main pieces of information concerning the application of transient absorption (TA) spectroscopy with sub-picosecond laser pulses. A description of the experimental apparatus and of some detection schemes are included together with the most common mathematical formulas utilized to analyze the signals. The results, recently obtained in our laboratory and presented here, concern the investigation of the excited state dynamics of simple molecular systems. Examples of the measurements of the relaxation processes occurring in the lowest excited states of some aromatic molecules will be discussed in order to show the potentiality of the technique.