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First measurements of the differential positronium-formation cross-sections

Positrons are the antimatter version of electrons and so their fate in a matter world is ultimately to annihilate. However, prior to this, a positron may combine with an electron to form a matter-antimatter hybrid called positronium. This is akin to a hydrogen atom with the proton replaced by a positron. Fundamental to our understanding of the physical universe, positron and positronium are these days also acknowledged as being fantastically useful in practical applications such as probing material properties and medical diagnostics. However, there is still much that we do not know for sure about the details of the interactions of these particles with ordinary matter. For example if, in a collision with an atom or molecule, a positron captures an electron, in which directions is the positronium likely to travel and with what probability? More...

Published: Jun 17, 2015 12:35:19 PM

CO2 Satellite

New calculations to improve carbon dioxide monitoring from space

How light of different colours is absorbed by carbon dioxide (CO2) can now be accurately predicted using new calculations developed by a UCL-led team of scientists. This will help climate scientists studying Earth’s greenhouse gas emissions to better interpret data collected from satellites and ground stations measuring CO2. More...

Published: Jun 15, 2015 10:29:10 AM

Watt Steam Engine

On quantum scales, there are many second laws of thermodynamics

New research from UCL has uncovered additional second laws of thermodynamics which complement the ordinary second law of thermodynamics, one of the most fundamental laws of nature. These new second laws are generally not noticeable except on very small scales, at which point, they become increasingly important. More...

Published: Feb 10, 2015 11:55:53 AM

Ultracold Gases

Prof Peter Barker
Dr Phil Jones
Prof Tania Monteiro
Prof Ferruccio Renzoni
Dr Gillian Peach

Our research programmes in cold atoms and molecules are both theoretical and experimental and range from developing methods for cooling, trapping to utilising cold atoms for understanding quantum chaos and statistical physics. We also study ultracold Bose and Fermi gases and their interactions.

Cooling atoms and molecules: We are exploring new methods for creating cold atoms and molecules. This includes cavity cooling, optical Stark deceleration for the creation of slow cold molecules and sympathetic cooling of molecules with cold atoms . Cold atoms trapped in periodic potentials (optical lattices) can be used to mimic the random motions of systems in equilibrium with a thermal bath.  Directed (ratchet) motion and a Brownian motor has been realised using these systems (Barker , Jones, Renzoni).

Quantum dynamics and chaos:  We investigate the theory for quantum dynamics of systems subjected to time periodic driving. Quantum chaos using cold atoms is one area of interest: eg, new examples of quantum suppression of chaotic diffusion; new types of quantum chaotic ratchets; the stability of BECs in these regimes. The  possibilities for manipulation of phase transitions by cold  atoms in optical lattices are also studied (Monteiro, Jones).

Ultracold Bose and Fermi gases:  Many-particle descriptions of pairing via Feshbach resonances are studied, as well as the production and probing of exotic few-body molecules, and photoassociation using coherent control. (Kohler).

To learn more about our work please follow the links below: