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 Nicolai Nygaard Institut for Fysik og Astronomi Aarhus Universitet Ny Munkegade, Bygn. 1520 (kontor 634) 8000 Århus C Denmark Telephone: +45 89 42 36 80 Fax: +45 86 12 07 40 Email: nygaard@phys.au.dk Web: www.phys.au.dk/~nygaard