Absolute timing of the photoelectric effect

Photoelectric effect timed by atomic clock

1 February 2019

An atomic stopwatch has clocked the photoelectric effect to within a few billionths of a billionth of a second.

The photoelectric effect, for which Albert Einstein was awarded his Nobel prize, occurs when a metal absorbs high-energy light and releases an electron. The reaction is so rapid that only the direction and energy of escaping electrons have been accurately measured, until now.

A team that included researchers from the Technological University of Munich stuck iodine atoms onto a tungsten crystal and hit them with X-rays. Iodine atoms react extremely quickly to X-rays so served as a stopwatch for the moment the X-rays hit the crystal’s surface, while a laser pulsing above the crystal measured the arrival time of the escaping tungsten electron. This enabled the researchers to calculate the photoelectric effect duration with attosecond (10⁻¹⁸ second) accuracy, and they observed tungsten generate photoelectrons in about 40 attoseconds.

Understanding photochemical reactions on different surfaces could help improve the efficiency of harvesting solar energy.

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References

1. Nature 561, 374–377 (2018). doi: 10.1038/s41586-018-0503-6