Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists from Bonn cool gas by laser bombardment

03.09.2009
First evidence that a method proposed 3 decades ago really works

In their experiment the scientists tested a completely new principle of cooling. For this, they used the property that atoms can be stimulated by light.

In this process an electron changes from its orbit around the atom's nucleus to an orbit that is further away. However, this is only successful if the incoming light has the appropriate colour. Red light has less energy than blue light. Therefore the 'push' which a red laser gives the electron may not be sufficient for lifting it to a higher orbit.

Atoms in a gas collide with each other regularly. The higher the pressure of the gas is, the more frequent the collisions are. 'In this process the electron orbits of the particles "bend",' Professor Martin Weitz from the Institute of Applied Physics explains. 'At the time of the collision, you therefore need less energy than normally in order to vault the electron into a high orbit.' After the collision the electron orbits become normal again. In order to then stay on the higher orbit, the electron has to 'borrow' the missing energy. 'To do so, it uses the kinetic energy of the atom, which becomes slower in this process,' Ulrich Vogl, a member of Weitz's team adds. Speed and temperature are two sides of the same coin – the slower the molecules in a gas move, the colder it is. So the laser bombardment results in the gas cooling down.

This elegant method was already proposed in 1978 by researchers from New York and Helsinki. However, their idea applied to gases of a not particularly high pressure and the experiments carried out in this way were not really successful. Researchers from Bonn have now heated a mixture of argon gas with traces of rubidium to 350 degrees Celsius and increased the pressure to 230 bars. 'Under these conditions we were able to stimulate the rubidium with a laser whose energy would have normally not been sufficient,' Martin Weitz says. 'While we were doing this, the gas mixture cooled down by almost 70 degrees within several seconds.'

With their experiment the physicists from Bonn wanted to demonstrate first of all that laser cooling works in general under pressure. 'But the whole process should also work with gases below room temperature,' Martin Weitz says confidently. 'Possibly even temperatures close to absolute zero can be achieved with this method.' There are already methods of laser cooling with which gases can be cooled to such low temperatures. However, they only work at extremely low pressures. The gas mixture used in Bonn was ten billion times more dense. Moreover, the new method permits much higher refrigeration capacities. It may therefore be possible to design new kinds of mini fridges on this basis.

High refrigeration capacity

The high refrigeration capacity is also what makes the process attractive for matter researchers. It allows gases to be brought into new, previously unexplored states of matter. As a result of the rapid refrigeration they might remain in a gaseous state at temperatures where they would normally be liquid. Similar effects are known from water, which can be cooled down to - 42 degrees Celsius without it freezing. If the cooling happens very quickly, even lower temperatures are conceivable. 'Supercooled' liquids and gases show interesting properties. Producing them is therefore of interest to many scientists.

Dr. Martin Weitz | EurekAlert!
Further information:
http://www.uni-bonn.de

More articles from Physics and Astronomy:

nachricht Applicability of dynamic facilitation theory to binary hard disk systems
08.12.2016 | Nagoya Institute of Technology

nachricht Will Earth still exist 5 billion years from now?
08.12.2016 | KU Leuven

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: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

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,...

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

Closing the carbon loop

08.12.2016 | Life Sciences

Applicability of dynamic facilitation theory to binary hard disk systems

08.12.2016 | Physics and Astronomy

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>