https://www.sciencedaily.com/releases/2019/08/190805112212.htm

In their experiment, whose results they report in a paper published today in Nature Physics, Mikhail Volkov and colleagues in the Ultrafast Laser Physics group of Prof. Ursula Keller exposed thin foils of the transition metals titanium and zirconium to short laser pulses. They observed the redistribution of the electrons by recording the resulting changes in optical properties of the metals in the extreme ultraviolet (XUV) domain. In order to be able to follow the induced changes with sufficient temporal resolution, XUV pulses with a duration of only few hundred attoseconds (10^-18 s) were employed in the measurement. By comparing the experimental results with theoretical models, developed by the group of Prof. Angel Rubio at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, the researchers established that the change unfolding in less than a femtosecond (10^-15 s) is due to a modification of the electron localization in the vicinity of the metal atoms. The theory also predicts that in transition metals with more strongly filled outer electron shells an opposite motion -- that is, a delocalization of the electrons -- is to be expected.

Ultrafast control of material properties