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 Water without windows: Capturing water vapor inside an electron microscope
13.12.2017 | Okinawa Institute of Science and Technology (OIST) Graduate University

nachricht Columbia engineers create artificial graphene in a nanofabricated semiconductor structure
13.12.2017 | Columbia University School of Engineering and Applied Science

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: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

A whole-body approach to understanding chemosensory cells

13.12.2017 | Health and Medicine

Water without windows: Capturing water vapor inside an electron microscope

13.12.2017 | Physics and Astronomy

Cellular Self-Digestion Process Triggers Autoimmune Disease

13.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>