When light strikes electrons in atoms, their state can change unimaginably quickly. Laser physicists in Munich have measured such a phenomenon - namely that of photoionization, in which an electron exits a helium atom after excitation by light - for the first time with zeptosecond precision. A zeptosecond is a trillionth of a billionth of a second (10-21 seconds). This is the greatest accuracy of time determination of an event in the microcosm ever achieved, as well as the first absolute determination of the timescale of photoionization.
If light hits the two electrons of a helium atom, one must be incredibly fast to observe what occurs. Besides the ultra-short periods in which changes take place, quantum mechanics also comes into play. ...
