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
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
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
Theoretical Physics of Molecules and Quantum Systems
The AMOPP group has a number of theoretical research programs including:
- Theoretical molecular physics (Prof Jonathan Tennyson)
- Quantum dynamics and quantum chaos (Prof Tania Monteiro)
- Ultracold molecules and collisions (Prof Jonathan Tennyson)
- Atoms and molecules in intense laser fields (Dr Carla Figueira de Morisson Faria and Prof Jonathan Tennyson)
Please read below for more details.
Theoretical molecular physics
The molecular theory group
develops methods based on first principles quantum mechanics for
studying the structure, spectra and collision properties of molecules.
Research in the group is a mixture of studying fundamental problems
such as ultra cold molecular collisions and electron and positron molecule collisions, and application of theoretical methods to key areas such as astrophysics and atmospheric physics, where as part of the CAVIAR consortium
we are trying to determine the physical basis of the so-called water
The image on the left shows an artists impression of extra solar planet HD189733b. Calculations by the molecular theory group led directly to the detection of water in the atmosphere of the hot Jupiter-like planet in 2007, the first molecule detected on an extra solar planet, see here for more details.
The molecular theory group also works alongside the Quantemol company producing software model electron polyatomic molecule interactions for a variety of applications including plasma physics.
More information about our theoretical molecular physics reseach can be found on the molecular theory group webpages.
Quantum Dynamics and Quantum Chaos
We have a program of work studying how
a quantum system behaves if the corresponding classical dynamics is chaotic:
'quantum chaos' is
important in a wide range of systems in atomic, molecular, optical, nuclear and mesoscopic
systems. At present we are working on three main projects:
For more information please see the Quantum Dynamics and Quantum Chaos group webpages.
Ultracold molecules and collisions
The formation of ultracold molecules is a new and rapidly developing area in the physics of quantum degenerate gases. The aim of our research is to theoretically understand the dynamics of the association of molecules and its interplay with the bulk motion in trapped Bose-Einstein condensates and quantum degenerate two component Fermi gases. The applications of our research are far reaching; they range from precise studies of two- and few-body ultracold collisions to the many-body physics of Cooper pairing of Fermions.
Our ongoing research includes topics such as:
Atoms and molecules in intense laser fields
When atoms and molecules are exposed to extremely strong laser fields
novel and exciting processes can take place. At UCL we have an ongoing
program of experimental and theoretical work studying these processes
such as above threshold ionization, high-order harmonic generation,
electron recollision, and non-sequential double ionization. In recent
years, understanding these processes has led to the possibility of
using ultrashort laser pulses to image molecular processes on the
attosecond timescale and the angstrom length scale simultaneously. The
theory underpinning our understanding of these processes is being
actively developed by Carla Faria, and Jonathan Tennyson is extending R-matrix methods to apply to these problems.