The photoelectric effect is one of the physical phenomena in the early twentieth^e century led to the formulation of quantum mechanics : when an atom exposed to radiation of sufficiently high frequency , part of the radiation energy is absorbed by an electron of the atom , electron s ‘ then escapes from the atom. The emission of the electron is so fast , so far, in the models, they considered instantaneous . An international team of physicists , including Max Planck Institute for Quantum Optics in Garching , Germany , has shown that the electron could be issued with a delay, and delay depend on the quantum state in which he was within the atom.

If a delay existed without being detected, it should be small , the order of several tens of attosecond ( one attosecond is 10^–18 second , or one billionth of a billionth of a second) . To highlight a delay of this order , the researchers used two synchronized ultrashort optical pulses . One , ultraviolet attosecond lasted a few decades , it will provide the electron sufficient energy to escape from . The other impulse, infrared flash is a little longer – a few femtoseconds ( one femtosecond is 10^–15 second ) – and more intense it is that which measures the delay of the electron. Here’s how.

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