Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Research Paper Illuminates How Light Pushes Atoms

22.08.2006
A research paper to be published in the 18 August edition of the journal Physical Review Letters reveals a new effect in the fundamental way that laser light interacts with atoms.

"Unlike water, which speeds up as it passes through a small nozzle, photons of light have less momentum at the center of a focused laser beam," says Kurt Gibble, an associate professor of physics at Penn State University and the author of the research paper. Gibble's theoretical paper analyzes the speed of an atom after it absorbs a photon of light and reveals the surprising effect that a photon in a narrow laser beam delivers less momentum to an atom than does a photon in a wide beam of light.

Einstein proposed that a light wave is made of photons that carry discrete packets of energy. "When a photon hits an atom, the atom recoils with a speed that is determined by the photon's momentum, similar to two balls colliding on a billiard table," Gibble explains. Physicists often think of a focused laser beam as the intense intersection of two or more infinitely wide light waves, and Gibble's discovery provides an important new understanding of what happens to an atom that is pummeled by photons coming from the different directions of these multiple intersecting light waves. "You might think that an atom would absorb a photon randomly from only one of the beams, but this paper shows that the atom feels the effect of the photons from all of the beams simultaneously and, surprisingly, that it recoils with a speed that is less than it would get from the momentum of any one of the infinitely wide photons."

Gibble's discovery has implications for the accuracy of atomic clocks, which are based on microwaves. "For a laser beam that is 1 centimeter in diameter, the sideways components of the photons act as microwave photons, which have a smaller energy and momentum than visible photons," Gibble explains. The world's most accurate atomic clocks use microwaves. "These microwaves produce sideways forces on the atoms in exactly the same way as a narrow laser beam," Gibble says. "With the traditional approach of treating the microwaves as being infinitely wide, you expect an error in the clock that is comparable to the current accuracy of the best atomic clocks, so this effect needed to be better understood." Gibble's new work demonstrates that the recoil from the microwave photons produces a smaller frequency shift than previously thought, meaning that the clocks actually can be more accurate. Gibble's research also reveals an important correction for the next generation of more precise tests of fundamental physics. Some of these tests use atom interferometers to measure precisely the recoil speed of an atom, which is used to determine the fine-structure constant--a fundamental description of how matter and electromagnetic energy interact. "The important thing is that we now understand much better some of the physics that is behind atomic clocks and atom interferometers," Gibble comments.

Support for this research was provided by the National Aeronautics and Space Administration and the Office of Naval Research.

Barbara K. Kennedy | EurekAlert!
Further information:
http://www.psu.edu

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>