Juliette Simonet

Ultrashort laser pulses grant access to an instantaneous and controlled creation of electrons and ions in a quantum gas. A single femtosecond laser pulse can ionize up to several thousand atoms, thus triggering the formation of strongly coupled ultracold plasmas.

We report on the observation of ultrafast electron cooling in an expanding micro-plasma from 5000 K to about 1 K within less than one picosecond. Our experimental setup allows measuring the electronic kinetic energy distribution with meV resolution. Furthermore, we have performed numerical simulations of the plasma dynamics that are in excellent agreement with the measurements and provide insights into the thermalization mechanisms on sub-nanosecond timescales.