German Scientists Measure How Fast an Electron Jumps, the Shortest Time Interval Ever Measured | Popular Science: "The team bombarded atoms of neon gas with near-infrared laser light in 10-15 second pulses and ultraviolet pulses of far shorter durations of just 180 attoseconds (remember, an attosecond is one billionth of one billionth of one second). The near-IR light served as an attosecond chronograph, measuring the time of UV impact and the time the electrons exited their orbits.
Their findings turned up two interesting results. For one, they found that electron ejection is not a “time zero” action as once presumed, but that excited electrons hesitate very, very briefly before leaving the atom. But perhaps more interesting, they found that electrons from different orbitals behaved differently, leaving the atom at slightly different times even though they were impacted simultaneously."