Direct measurement of the formation length of photons

Feb 28, 2012

How long does it take an electron to form a photon? The answer would normally be: so short a time that it cannot be measured. However, the international CERN team responsible for experiment NA63 -- mainly staffed by physicists from Aarhus University -- has now succeeded in dragging out the process, thereby making it measurable.

They achieved this by utilising the phenomena of objects moving slower and shortening in length from Einstein's , along with two pieces of gold foil and a micrometre screw.

In Niels Bohr's model of the atom, electrons orbit the in 'shells' – the so-called stationary states. Light is emitted by a quantum leap between a high-lying shell and one nearer the nucleus. However, it is impossible to find the electron between the two shells, so it could be thought that the light emission process itself was instantaneous: the electron is in the outer shell and immediately after sending out light, it is in the inner one.

However, Associate Professor Ulrik I. Uggerhøj, PhD student Kristoffer K. Andersen, Aarhus University, and the other NA63 members actually found that it takes the electron a measurable amount of time to emit light.

By letting the electron pass two very flat gold foils stretched out at a distance that can be measured with a precision of a few micrometres, they can 'force' the electron to emit shortwave light in a well-defined area. The distance between the foils corresponds to the length taken to form the .

The results have been published in the journal Physical Review Letters under 'highlights'.

Explore further: New filter could advance terahertz data transmission

More information: prl.aps.org/abstract/PRL/v108/i7/e071802

add to favorites email to friend print save as pdf

Related Stories

New research improves quality of free electron laser

Jun 02, 2011

The free electron laser is the next step in the development of equipment to help us see the structure of materials. Nino Čutić at MAX-lab in Lund, Sweden, has done a PhD in further improving the test free electron ...

New record for measurement of atomic lifetime

Sep 07, 2011

Researchers at the Niels Bohr Institute have measured the lifetime of an extremely stable energy level of magnesium atoms with great precision. Magnesium atoms are used in research with ultra-precise atomic ...

Recommended for you

Breakthrough in OLED technology

38 minutes ago

Organic light emitting diodes (OLEDs), which are made from carbon-containing materials, have the potential to revolutionize future display technologies, making low-power displays so thin they'll wrap or fold ...

Throwing light on a mysterious human 'superpower'

3 hours ago

Most people, at some point in their lives, have dreamt of being able to fly like Superman or develop superhuman strength like the Hulk. But very few know that we human beings have a "superpower" of our own, ...

New filter could advance terahertz data transmission

Feb 27, 2015

University of Utah engineers have discovered a new approach for designing filters capable of separating different frequencies in the terahertz spectrum, the next generation of communications bandwidth that ...

The super-resolution revolution

Feb 27, 2015

Cambridge scientists are part of a resolution revolution. Building powerful instruments that shatter the physical limits of optical microscopy, they are beginning to watch molecular processes as they happen, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.