April 03, 2020
11:00 am
Louvain-La-Neuve
Auditorium Jean-Baptiste CARNOY (B059)
Attosecond soft-X-ray spectroscopy
in the gas and liquid phases
Prof. Hans Jakob Wörner
!! This seminar has been postponed at a later date not yet defined. !!
Attosecond time-resolved spectroscopy has the potential to address fundamental open questions in chemical sciences. Although the first two decades of research have led to very important advances towards this goal, the techniques of attosecond spectroscopy still need to overcome two gaps. The first gap is the complexity gap, i.e. the challenge of applying attosecond spectroscopy to complex molecules. A promising approach to overcome the complexity gap consists in exploiting the element-, site- and spin-sensitivity of X-ray spectroscopy. We have recently demonstrated the potential of table-top X-ray absorption spectroscopy with a water-window high-harmonic source, observing the temporal evolution of unoccupied molecular orbitals, as well as molecular shape resonances during chemical reactions [1]. Compressing the mid-infrared driving pulses to less than two optical cycles, we have demonstrated the extension of this table-top source to fully cover the oxygen K-edge with fluxes sufficient for time-resolved measurements [2]. Using the same technique, we have also demonstrated the generation of isolated attosecond pulses, which have established a new record of the shortest light pulses ever measured (43 attoseconds) [3]. In our most recent work, we have applied attosecond soft-X-ray spectroscopy to observe electronic dynamics in several molecules. The second gap is the extension from the gas to the liquid phase, which is the relevant phase for the vast majority of chemical and biophysical processes. I will discuss the first realization of femtosecond time-resolved soft-X-ray absorption spectroscopy of liquids with a high-harmonic source [4]. In our most recent collaborative work, we have extended these measurements to study ionization-induced dynamics in several molecular liquids. These combined developments set the stage for attosecond time-resolved studies of molecular systems of chemical complexity.