Kienberger Group

Attosecond beamline at the Chair of Laser and X-ray Physics at TUM. Generation of sub-4-fs intense NIR pulses and > 100 eV attosecond pulses for time resolved measurements of electron dynamics.

Our group's activities aim at investigating processes inside atoms, molecules and solids on the shortest timescale reached so far, the attosecond timescale. New insight into ever smaller microscopic units of matter as well as in ever faster evolving chemical, physical or atomic processes pushes the frontiers in many fields in science. The interest in these ultrashort processes is the driving force behind the development of sources and measurement techniques that allow time-resolved studies at ever shorter timescales.


Ultrafast laser spectroscopy of quantum dynamics

Field assisted photoemission of different electrons from a solid (W) covered with a monolayer (I). The absolute transport time of en electron through defined nanostructures is measured (click to enlarge).

Pump-probe experiments turned out to be the most direct approach to time-domain investigations of fast-evolving microscopic processes: A short excitation pulse sets the process going and a probe pulse takes snapshots of subsequent stages of its evolution. Accessing atomic and molecular inner-shell processes directly in the time-domain has until recently been frustrated by the required combination of short wavelengths and sub-femtosecond pulse duration. A solution of this problem, namely the concept of light-field-controlled XUV photoemission allows to substitute either the XUV pump or the XUV probe pulse by a strong few-cycle laser field, in other words, to employ the XUV pulse as a pump and the light pulse as a probe or vice versa. The basic prerequisite, namely the generation and measurement of isolated sub-femtosecond XUV pulses synchronized to a strong few-cycle light pulse with attosecond precision, opened up a route to time-resolved inner-shell atomic as well as molecular spectroscopy with present day sources [1,2].

In general, the experimental tools used in the group are pump/probe techniques in various constellations (e.g. 2-color) measured with time resolved spectroscopic tools (absorption spectroscopy, photoelectron and ion spectroscopy). Many different sources are being used and developed ranging from the infrared (optical parametric amplification techniques, OPA) to visible (chirped pulse amplification techniques, CPA) [3], ultraviolet (nonlinear optics, NLO), extreme ultraviolet (high-order harmonic generation, HHG) [1,2] to x-rays (free electron lasers, FEL) [4].

The goal of this research group is to use femtosecond and attosecond technology and methods to resolve ultrafast processes in condensed matter sciences by providing direct access to the motion of electrons in molecular and solid state systems.

Efforts are undertaken to control and measure the attosecond-scale charge hopping that takes place by the movement of bound electrons between the nuclei of simple molecules. In these complex systems a charge transfer may solely be driven by electron correlation.

Of special interest are electronic transport and bandstructure effects in solids [5-7] and nanostructured systems [8], electronic correlation [9] and dephasing.

The research is conducted at the chair of Laser and X-Ray Physics (E11) at the Physics Department of TUM, at the Max-Planck-Insitute of Quantum Optics (Max-Planck-Fellow) and at beamtimes at large scale facilities (eg. LCLS at Stanford Linear Accelerator Center).


Selected publications

  1. R. Kienberger et al., Science, 297 (2002)
  2. R. Kienberger, et al., Nature, 427(2004)
  3. T. Wittmann et al., Nature Physics 5 (2009)
  4. W. Helml et al., Nature Photonics 8 (2014)
  5. A. Schiffrin et al., Nature  507 (2014)
  6. Sommer et al., Nature 534 (2016)
  7. M.S. Wagner, et al.,  Phys. Chem. Chem. Phys. 17 (2015)
  8. S. Neppl et al., Nature 517 (2015)
  9. M. Ossiander et al., Nature Physics 13 (2016)

Prof. Reinhard Kienberger

Address:

TUM Physics Departement, E11

James-Franck-Str. 1

D-85748 Garching

 

reinhard.kienberger(at)tum.de

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