Artistic illustration of how a train of attosecond pulses (blue) and a IR-laser pulse (red) interact with electrons in the two outer shells of Neon. The picture is made by Marcus Isinger.


Our research focus on the use of numerical methods to treat many-body systems with a high degree of sophistication. We use a variety of many body- methods from configuration interaction, where three-, and even four-body systems, are treated virtually exactly, to diagrammatic methods where classes of diagrams can be summed to all orders. When needed, we work in the framework defined by the Dirac equation and account for the effects of retardation and magnetic interaction on electron correlation. Our present main interests are the interpretation and quantitative description of experimental observations with attosecond light sources and how ultra-intense laser pulses interact with matter.

The attosecond time-scale is typical for electrons in atoms and molecules. That is the time-scale on which they react and rearrange when their surrounding changes. Today laser pulses with a duration of around 100 attosecond, and below, are made in many labs around the world and there is a strong drive to use them to capture electron dynamics in real time. However, electrons are truly quantum mechanical objects. They are not at all classical particle with defined paths in space  and we cannot "film" them in the usual sense of the word, regardless of how short pulses that are used for the snap-shots. What attosecond pulse techniques do allow though, is measurements of both phase and amplitude of electronic wave packets, and thus to reconstruct the complex, time-dependent electron wave function. For the interpretation of these type of experiments theory plays a decisive role. This is the main focus of our research. In addition we work on general aspects of light matter interaction, electron-ion recombination and structure problems in connection with heavy elements, autoionizing states and artificial atoms (quantum dots and rings).

Attosecond techniques can be used to quantify the delayed response to photoabsorption.
This is  a subject we have worked a lot with   - see more in this Science article