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!
Seeing the quantum future... literally
16.01.2017 | University of Sydney
Airborne thermometer to measure Arctic temperatures
11.01.2017 | Moscow Institute of Physics and Technology
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering