Ursula Keller

Professor Ursula Keller

Department of Physics, ETH Zurich
2015 Frew Fellow of the Australian Academy of Science

Attosecond Ionization Dynamics and Time Delays
The basic motivation is to understand and ultimately control how matter functions at the electronic, atomic and molecular level. Initially our focus is on the question how quanta of energy and charge are transported on an atomic spatial and attosecond time scale. In principle, time dependent-processes in quantum mechanics are described by the time-dependent Schrödinger Equation (TDSE). The challenge is that the TDSE in most cases cannot be solved without approximations and that time is not an operator and therefore not a direct observable.

Semi-classical models, on the other hand, seem to explain suprisingly well many current attosecond measurements. Attosecond measurements have advanced rapidly with reproducable and high-quality data, allowing for very fundamental tests for our current understanding and models in time-dependent quantum mechanics. This talk will review the recent progress in attosecond ionization dynamics and time delays in photoemission and tunnel ionization. Following the peak of an electron wavepacket (i.e. the group delay) for determining time delays can be tricky and often misleading.

We will discuss why in the multi-photon or tunnel ionization regime the group delay (or the related Wigner delay) gives the wrong explanation for the measured delay, whereas in the single-photon ionization regime we can show experimentally that the Wigner time delay can explain the general trend correctly although it does not capture all the observed features.

Ursula Keller a tenured professor of physics at ETH Zurich since 1993 (www.ulp.ethz.ch), and currently also a director of the Swiss multi-institute NCCR MUST program in ultrafast science since 2010 (www.nccr-must.ch). Born in Switzerland 1959, she received a „Diplom“ at ETH Zurich in 1984, a Ph.D. at Stanford University USA in 1989, was a Member of Technical Staff at Bell Labs USA 1989 to 1993, a visiting professor at the Lund Institute of Technologies (2001) and at UC Berkeley (2006). She has been a co-founder and board member for Time-Bandwidth Products (acquired by JDSU in 2014) and for GigaTera (acquired by Time-Bandwidth in 2003). 

Her research interests are exploring and pushing the frontiers in ultrafast science and technology. Awards include the OSA Charles H. Townes Award (2015), LIA Arthur L. Schawlow Award (2013), ERC advanced grant (2012), EPS Senior Prize (2011), OSA Fraunhofer/Burley Prize (2008), Leibinger Innovation Prize (2004), and Zeiss Research Award (1998). OSA, SPIE, IEEE and EPS Fellow, member of the Royal Swedish Academy of Sciences, Academy Leopoldina and Swiss Academy of Techical Sciences. She supervised and graduated more than 60 Ph.D. students. According to Web of Science (23. Feb. 2015) >15'000 citations and an h-index of 66.