During the conversion of light into electricity, such as in solar cells, a large part of the input light energy is lost. This is due to the behaviour of electrons inside of materials. If light hits a material, it stimulates electrons energetically for a fraction of a second, before they pass the energy back into the environment. Because of their extremely short duration of a few femtoseconds—a femtosecond is one quadrillionth of a second—these processes have hardly been explored to date. A team from the Institute of Experimental and Applied Physics at Kiel University (CAU), under the direction of Professor Michael Bauer and Professor Kai Roßnagel, has now succeeded in investigating the energy exchange of the electrons with their environment in real time, and thereby distinguishing individual phases. In their experiment, they irradiated graphite with an intense, ultrashort light pulse and filmed the impact on the behaviour of electrons. A comprehensive understanding of the fundamental processes involved could be important in future for applications in ultrafast optoelectronic components. The research team has published these findings in the current edition of the journal Physical Review Letters.