Single sub-fs XUV pulses: Generation and measurement

The change from a zero transition to the maximum amplitude of the electric field of visible light lasts shorter than one femtosecond (1 fs = 10 ^-15 s). By precisely controlling the hyperfast electric field oscillations in a short laser pulse we developed a measuring apparatus - the Atomic Transient Recorder (ATR) - like an ultrafast stopwatch. This apparatus is capable of measuring the duration of atomic processes with an accuracy of less than 100 attoseconds (1 as = 10 ^-18 s) which is the typical duration of electronic processes (transients) deep inside atoms. A 250-attosecond X-ray pulse initiates the atomic process to be measured and the attosecond stopwatch at the same time. This new measuring method now allows for the first time the observation of ultrafast processes in the electron shell of atoms.