Prof. Thomas Stöhlker.

Atomic Physics in Extreme Coulomb & Laser Fields

Prof. Thomas Stöhlker.
Image: Jan-Peter Kasper (University of Jena)
Prof. Dr. Thomas Stöhlker Prof. Dr. Thomas Stöhlker Image: Private

Prof. Dr. Thomas STÖHLKER

Phone: +49 3641-9-47600

Prof. Stöhlker is the director of the Helmholtz Institute Jena and the representative of the APPA research branch (Atomic Physics, Plasma Physics, Materials Research) at GSI, Helmholtz Centre for Heavy Ion Research in Darmstadt. He is a member of “From Matter to Materials and Life”, and the speaker of “From Matter to Materials and Life”, both research programmes of the Helmholtz Association.

This group focuses on the exploration of the particle dynamics in the realm of strong and critical Coulomb and photon fields with particle emphasis on Quantum Electrodynamics. For this purpose highly charged ions and strong laser fields and their combination are particularly well suited but require the development of dedicated diagnostics and instrumentation. As examples, within our experimental campaigns various x-ray detection systems such as 2D/3D position-sensitive and energy-dispersive detectors, crystal spectrometers, x-ray CCDs, novel x-ray polarimeters, and micro-calorimeters are getting developed and used as well as ion sources, storage rings, and traps to study ions in intense laser light.

Research Areas

Prof. Stöhlker’s research interests are focused on electron dynamics in strong and extreme fields, with particular emphasis of the effects of quantum electrodynam-ics (QED):

  • Experiments on bound-state QED and the atomic structure of few-electron ions at high-Z
  • Radiative processes in collisions of relativistic particles (ions and electrons)
  • Collision dynamics involving heavy ions
  • Light-matter interaction in the strong-field regime
  • Application of advanced x-ray and electron-detector and spectrometer concepts

Teaching Fields

Prof. Stöhlker’s teaching is focused on the physics of simple atomic systems, including the atomic structure, atomic collisions, and fundamental aspects such as QED and parity violation. He gives courses and seminars in: 

  • Key experiments in modern atomic physics
  • The interaction of high-energy radiation with matter
  • Photonic processes in highly ionized matter

Research Methods

Prof. Stöhlker runs sophisticated setups for photon, x-ray, electron, and ion spectroscopy which are used for the experiments at storage rings, traps and synchrotrons, including:

  • X-ray spectrometers of transmission and reflection type
  • Micro calorimeters
  • Dense-cluster targets for H2, He, N2, Ne, Ar, Xe

Recent Research Results

One- and two-electron ions provide an ideal testing ground for fundamental atomic structure theories, for the investigation of QED (self energy and vacuum polarization) as well as relativistic and correlation effects [1]. A new experiment at CRYRING@ESR, the first installation to be made available at the FAIR accelerator and storage ring complex currently under construction near Darmstadt, aims to determine the ground-state Lamb shift in hydrogen-like uranium with an accuracy that substantially exceeds 1%. This will provide the most stringent test of bound-state QED for one-electron systems in the strong field regime approaching the Schwinger limit (1016 V/cm). At extreme magnetic fields, meanwhile, substantial progress was made in 2017 when an experiment conducted on 209Bi82+,80+ improved the experimental precision of the socalled specific difference between the hyperfine splittings by more than an order of magnitude while finding a stillunexplained 7-σ deviation from theoretical predictions [2]. Current activities in these fields focus on the application of novel low-temperature bolometers for the hard X-ray regime. For polarization studies of hard x and γ radiation, the application of Compton scattering is another promising approach. Experiments utilizing novel 2D strip or pixel detectors focus on the study of photonic electron transitions and scattering processes in the strong-field domain (characteristic radiation, Rayleigh scattering, electron  bremsstrahlung and recombination radiation) where spin effects are important and provide detailed information about the quantum dynamics in the strong-field domain [3].

[1] Gassner et al., New J. Phys. 20, 073033 (2018).
[2] Ullmann et al., Nat. Commun. 8, 15484 (2017).
[3] Blumenhagen et al., New J. Phys. 18, 103034 (2016).

link to the Stöhlker group

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