4. Non-equilibrium time-resolved spectroscopy

The equilibrium spectroscopy described above opens the way to many important applications. For example, there is a device capable of discriminating the nature (composition, thickness) of pharmaceutical tablets, which can be directly integrated into a production line.

However, in many cases, the study of the dynamic aspect of processes is either more convenient to give a reading or a representation of the phenomenon under consideration, or quite simply necessary when the transience of the objects studied leads to very short time scales (< ns-ps). To illustrate the first case, if we consider two very close resonances, we must have sufficient resolution in the spectral domain to be able to separate these two components. But in the time domain, we can equivalently measure the beat of these two components and thus extract the same amount of information: the temporal...