Zeptosecond birth time delay in molecular photoionization

The travel time of light in a molecule There is currently considerable interest in experimental studies of various ultrafast processes. Of particular interest are the real-time dynamics of photoionization, one of the most fundamental processes caused by the light-matter interaction, in which the absorption of a photon leads to the ejection of an electron and the formation of anion. Using an electron interferometric technique, Grundmann et al. report a birth time delay on the order of a few hundred zeptoseconds between two electron emissions from the two sides of molecular hydrogen, which is interpreted as the travel time of the photon across the molecule. The proposed technique is generally applicable to more complex systems, and further studies are necessary to support this interpretation. Science , this issue p. 339