McGill.CA / Science / Department of Physics

Physical Society Colloquium

Attosecond Ionization Dynamics and Time Delays

Ursula Keller

Physics Department
ETH Z�rich

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.

Friday, April 7th 2017, 15:30
Ernest Rutherford Physics Building, Keys Auditorium (room 112)