Eos is our latest development for transient absorption spectrometry. It is a broadband optically gated flash photolysis spectrometer designed to work with an amplified femtosecond laser. Its patent pending design utilizes a photonic fiber for probe light generation. The instrument response function is <500 ps. The probe wavelength range is 400-1700 nm. The pump pulse energy required for Eos is not higher than in a typical femtosecond transient absorption experiment. The probe focal spot in the sample is comparable to that in a typical femtosecond transient absorption experiment.

For the researchers using femtosecond transient absorption for studying ultrafast kinetics of photoinduced processes it is often desirable to extend the time window of investigation beyond several nanoseconds. The most widely used method in this case was Nanosecond Flash Photolysis. This technique requires a dedicated Q-switched laser with accompanying wavelength conversion equipment, laser table, additional flash photolysis spectrometer, etc. Outside of the need to set up an additional laser spectrometer, the main disadvantage of this method is in a relatively low time resolution – a typical IRF in the nanosecond flash photolysis experiment is 7-10 ns. Therefore even when combined the above two methods do not provide continuous temporal coverage from femto- to milliseconds. The figures below illustrate the advantage of using Eos over conventional nanosecond flash photolysis setup. The kinetic data used in the examples below represent transient absorption profile of ZnTPP in toluene at 568 nm. This wavelength corresponds to absorption of the singlet excited state of the porphyrin.