X-ray stopwatch can measure durations of just attoseconds

The duration of short ångström-wavelength X-ray pulses, which lasted merely 170 attoseconds, has finally been measured accurately. The optical system designed for precision pulse duration metrology can be used as a ‘stopwatch’ to measure the rapid motion of electrons inside atoms and molecules, too. Short pulses generated by the system could be used to observe electrons moving around atomic nuclei.