N.B. We are starting a series of talks where "senior scientists" at IFA give a broad overview of their activities. Today's seminar is the first talk in this series.

Speaker: Lars Bojer Madsen (IFA)

Title: News from the ultrastrong and ultrafast: Theoretical femto- and attosecond science in Aarhus

Time: Today, 15.15

Place: Fysisk Auditorium

Abstract:

The description of quantum systems driven far from equilibrium presents one of the truly open challenges to theoretical low-energy physics. The situation becomes even more challenging when the driving source, in our case an intense light field, changes on a time scale that is similar to the natural time-scale of the dynamics in the systems under investigation. The reaction of quantum systems to strong external fields continuously presents new puzzles. Numerous examples show that techniques like the time-dependent density functional theory (TDDFT), or the time-dependent multi-configurational Hartree-Fock theory (TDMCHF) face severe problems. Solving the time-dependent Schrödinger equation numerically even for a 2-electron system is presently not possible for strong femtosecond laser pulses. Not even the problem of two-photon double ionization of the helium is solved. 

In the talk, I will show that it is nevertheless possible to formulate theory with predictive power, and I will show examples of research performed in the “New Light Source” group. I will discuss some of the basic theoretical concepts we use to describe the strong-field driving of atoms, molecules, and surfaces, and I will present a few selected examples: (i) ionization of (oriented) molecules by tunnelling theory and time-dependent Schrödinger equation, (ii) theory for time-resolved attosecond photoelectrons spectroscopy, and (iii) Monte Carlo wavepacket theory for dissociative ionization. 

Peter Staanum and Nicolai Nygaard