February-2018 Colloquium

Date : 07-02-2018
Time : 16:00:00
Speaker : Prof. P. C. Deshmukh
Venue : K. R. Ramanathan Auditorium, PRL


Einstein’s insightful analysis of the symmetry in the laws of electrodynamics changed our perception of space and time in a manner that continues to challenge common intuition. Even as time is not an observable, and perhaps not comprehensible, time-intervals are measurable. Physical atomic processes occur at ultra-fast speeds over attoseconds. In this talk, the Wigner-Eisenbud-Smith (WES) measure of time delay in atomic dynamics will be introduced. Exploiting the time-reversal symmetry, the WES time-delay is well-adapted to estimate the time-delay in the atomic photoelectric effect. Einstein’s explanation of photoionization laid the very foundation of the quantum theory. For over a hundred years, it was considered to be an ‘instantaneous’ process, but in the last decade, there have been pioneering studies, both experimental and theoretical, in which photoionization time-delays on the attosecond time scale have been reported. These are of importance for the atomic-clock technology, and to understand fundamental relativistic effects and many-body electron-correlations in atomic dynamics. This research field is very young, yet quite vast. This talk will provide a brief introduction to this exciting field and discuss our understanding of the photoionization WES time-delay, and its anisotropic character, especially in the energy regions of the Cooper-minimum, and also in the energy regions of autoionization resonances, and the shape resonances.