The interaction of materials with electromagnetic fields gives rise to excited-electron populations that evolve and decay over ultrafast (femtosecond to picosecond) time scales. These dynamic processes and the energy redistribution of the photoexcited charge carriers following the photoexcitation lie at the very heart of some of the most interesting light-induced physical phenomena, such as photocatalysis, photosynthesis, solar energy conversion and many more.
The knowledge of the ultrafast dynamic evolution of the electronic energy distribution following an impulsive photoexcitation would surely represent a major step forward in understanding and possibly steering light-induced phenomena in matter.
In a recent article published in Small, a team from CNR (SPIN, IOM, ISM and NANO), along with UniGe, PoliMi and UniMi, has succeeded in directly monitoring the ultrafast evolution of the hot-electron population in impulsively photoexcited plasmonic Au nanoparticles with sub-picosecond resolution.
Measuring the thermally-equilibrated fraction of the electron gas, the authors show that the ultrafast temperature evolution peaks more than 500 fs after the exciting radiation pulse, a time when all the energy “stored” in hot, non-thermal carriers has been transferred to the Fermi sea, and the ion lattice of the excited material is still “cold”. The measurements, performed by high-harmonic induced ultrafast photoemission at the SPRINT lab @Elettra (TS), will help to understand in more depth the ultrafast electronic processes that govern the excited-matter relaxation, and refine the related theoretical models.
Link to the article: https://doi.org/10.1002/smll.202100050
Link to CNR news: https://www.cnr.it/it/comunicato-stampa/10382