Researchers use visible light pulses to catch electrons in the act of emitting photons

New Scientist : In 2008, Eleftherios Goulielmakis of the Max Planck Institute of Quantum Optics in Garching, Germany, and his colleagues created the shortest ever pulses of light, with a duration of just 80 attoseconds (10⁻¹⁸ s). However, they used extreme UV (EUV) light, which is so energetic that it can strip electrons away from an atom entirely, rendering it useless for measuring the responses of electrons to outside stimuli. Now, Goulielmakis’s team has created the shortest ever pulses of visible light, with a duration of 380 attoseconds. Visible light does not strip electrons from around an atom; rather, it excites them just enough that they emit their own photons. The attosecond flashes were created by merging light pulses that were the same wavelength but slightly out of phase. Their interference cancels out all but small parts of the pulses. The 380-attosecond pulse was short enough to act like a camera flash, which allowed the researchers to catch the emission of UV photons from electrons orbiting krypton atoms. That emission took place just 115 attoseconds after the electrons were excited. It is the first time that researchers have been able to both excite an electron to emit a photon and directly measure the time it takes.