Zeptoseconds: the smallest ever unit of measurement used to describe time

In the late 1990’s, the term femtosecond was coined as a new unit of measurement in order to describe the speed at which bursts of laser light cause certain molecules change their conformations. Until recently, this phenomenon held the record for the shortest event ever recorded, and the femtosecond was the smallest unit of measurement used to describe time. 

            This record was broken on October 16^th by German physicist Reinhard Dörner. Dörner was born in 1961 and graduated from the JWG University of Frankfurt with a dual degree in physics and philosophy in 1988, at the age of 27. Dörner went on to complete his PhD in physics, also from the JWG University of Frankfurt, before spending part of the 1990’s working in California at the Lawrence Berkeley National Laboratory. Dörner has held a faculty position at the institute of nuclear physics at Goethe University Frankfurt since 2002. He has published over 420 papers involving topics including spectroscopy, atomic and ionization physics, the photoelectric effect, and the very same femtosecond laser technique popularized over twenty years ago, which his new discovery builds on. Dörner also developed the COLTRIMS reaction microscope, which is the tool of choice to observe ultrafast chemical reaction progress. This works by making use of patterns of ejected electrons and photons to create a percept of these processes.  

            Dörner’s latest breakthrough came when he measured the average time it takes for a single photon to cross the length of a hydrogen atom. Hydrogen exists in nature as a diatomic species (H₂). The two atoms are linked by a covalent bond, which is two aligned electrons. A device capable of exciting a single photon to X-rays wavelength was used to fire the single photon at the diatomic hydrogen. One single X-ray photon carries enough energy to excite both electrons to the point where they are ejected out of the diatomic hydrogen molecule. Ejection of the first electron results in measurable waves being created as the electron leaves. The same type of waves occur from photon contact with the electron bound to the second hydrogen atom quickly after. These two wave patterns, as well as the orientation of the hydrogen atoms can be measured using Dörner’s own COLTRIMS microscope. Dörner then used this data to determine the distance between the time the two wave patterns are sensed; which can be attributed to the difference in time from when the photon comes in contact with the electron belonging to the first hydrogen atom, and then the second. The time it takes for the photon to cross this distance, moving at the speed of light, was measured to be 247 zeptoseconds. This is equal to 2.47 x 10^-19seconds, and to date, represents the fastest event to ever be measured. So fast in fact, that the term zeptosecond was coined in order to describe the time elapsed using a unit with a magnitude greater than 1.

 

Sources:

1.     Staff, S. (2020, October 16). Zeptoseconds: New world record in short time measurement. Retrieved October 27, 2020, from https://phys.org/news/2020-10-zeptoseconds-world-short.html

2.     Physik Fachbereich 13. Retrieved October 27, 2020, from https://www.uni-frankfurt.de/45139800/Doerner