Kirchhoff Institute for Physics

Physikalisches Kolloquium

2. December 2022 5:00 pm  Folding the World: Infinite growth on a finite planet

Prof. Anders Levermann, Ph.D., Potsdam-Institut für Klimafolgenforschung, Folding the World: Infinite growth on a finite planet Prof. Dr. Anders Levermann Institut für Klimafolgenforschung, Potsdam We are at the end of an age – the age of expansion – and we need a new narrative for the next step. The limitations of our physical Earth collide with the necessity of rapid societal development. Accepting the harsh reality of both, we face a dilemma. The desperate call for renunciation and recession is understandable but counterproductive, because it does not resolve the dilemma. Where economists struggle, physicists know the answer: there is infinite opportunity in finite space. Therefore the mathematical concept of folding could provide a solution, because it allows for infinite motion in a finite world – through growth into diversity. Not growth into more, but into different – and not theoretically or esoterically but in a practical, applicable manner. more...

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Special CQD Seminar (funded by STRUCTURES) , November 30, 2022, 5 p.m., KIP, INF 227, Hörsaal 2

Dr. Christian Ott, Max-Planck-Institut für Kernphysik, Heidelberg, about:

Site-specific and state-resolved coherent quantum control of atoms and molecules

 

Using intense ultrashort laser pulses with a duration across the femtosecond and attosecond timescale, it is possible to couple and control multi-electron transitions which involve short-lived states in atoms and molecules. Their extreme-ultraviolet (XUV) and x-ray absorption spectra hereby encode the time-resolved dynamics with state-specific spectroscopic information about the relevant quantum states. In this talk, I will first provide an overview how we extract quantum-dynamics information from spectral absorption line shapes. We will discuss for instance the laser-controlled transformation of Fano to Lorentzian spectral line shapes of a correlated two-electron transition in helium, and how its absorption profile coherently builds up on the femtosecond timescale. We will further apply these concepts to nonlinear absorption spectroscopy with free-electron lasers and discuss XUV-induced energy shifts of strongly coupled states, e.g., in helium and neon atoms. Finally, we will also look at time-resolved measurements with XUV-pump – XUV-probe absorption spectroscopy to resolve the state-specific dynamics in small molecules, accessing structural dynamics from the perspective of individual electronic states. With all these experiments, we explore new methods of nonlinear light-matter interaction for the quantum control of atoms and molecules down to the natural attosecond timescale of the electron motion and coherently addressing specific transitions of individual constituents within the larger quantum system.

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