The duration of photoemission can be measured precisely following a series of new experiments at the Max Planck Institute for Quantum Optics.

The term ‘Quantum Jump’ refers to a concept when quantum particles jump from one energy level to another. These jumps are tiny, indivisible, and instantaneous. Despite the fact that scientists watch them appear to blink on and off, they have come up with precise methods to measure this process. For instance, the duration of the famous ‘Photoelectric Effect’ can be measured precisely with these new techniques. Albert Einstein was the first individual to explain this phenomenon to the world in 1905. He told the world that electrons are released from the surface of certain materials whenever light falls on them. He also discussed the smallest units of light and called them ‘Light Quanta’. Later on, their name was changed to Photons.

According to the latest research, a team of international researchers determined the duration of photoelectric effect at a Tungsten surface. A collaboration between different research groups from Munich, Garching, and Berlin and a researching team at the Vienna University of Technology led to this amazing discovery. Joachim Burgdörfer, a Professor at the Institute for Theoretical Physics of the Vienna University of Technology described their work in the following words:

“With the help of ultra-short laser pulses, it has been possible in recent years to gain for the first time insight into the timing of such effects. Together with our colleagues from Germany, for example, we were able to determine the time interval between different quantum jumps and show that different quantum jumps take different amounts of time.”

The photoelectric effect has numerous applications in a number of technical fields because it occurs on a time scale in the attosecond (a billionth of a billionth of a second) range. It is used for converting data from fiber optic cable into electric signals. Similarly, solar cells make use of this technology. Having said that, it was not possible, previously, to determine the absolute duration. Due to this reason, scientists relied on time differences because it is extremely difficult to find a clock which ticks precisely at the beginning of a quantum jump.

Things changed recently when a combination of several theoretical calculations, experiments, and computer simulations provided scientists with the methods to measure these durations precisely. The researchers progressed in a step-wise manner to achieve this glory. First of all, they used laser pulsars to extract electrons out of helium atoms. Professor Christoph Lemell referred to that and said,

“The helium atom is very simple. In this case, we can accurately calculate the time evolution of the photoemission. For more complex objects, such as metal surfaces, this would not be possible even with the best supercomputers in the world.”

Consequently, these helium atoms were selected as a reference clock. In the following experiment, the ‘Iodine Clock’ was calibrated by comparing its photoemission with that of the helium. Once this was done, the researching team was all set for measuring the photoemission of electrons from a tungsten surface (the ultimate goal of the research). Ultra-short laser pulsars were shot at a tungsten surface having a layer of Iodine atoms spread over it and these atoms served as a reference clock for measuring the photoemission of the metal. The laser pulse initiated the process during which the electrons escaped their atoms and jumped into a different quantum level. It allowed them to reach and leave the tungsten surface. Professor Florian Libisch mentioned the benefits of using tungsten by saying,

“In tungsten, the duration of this process can be studied particularly well because the interface of the material can be defined very precisely there. The tungsten surface is an excellent finish line for electron-time measurement.”

The results of this experiment showed that the duration of the photoemission is variable as it depends upon the initial state of the electrons. For conduction band electrons, it was 45 attoseconds while it increased up to 100 attoseconds for the electrons lying in the inner shells. Talking about the future prospects of this research, Joachim Burgdörfer said,

“It is an exciting field of research that provides remarkable new insights — for example into surface physics, and into electron transport processes inside materials. It gives us the opportunity to study important physical processes with an accuracy that would have been inconceivable a few years ago.”