Mainz 2017 – scientific programme

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A: Fachverband Atomphysik

A 22: Attosecond Science

A 22.5: Talk

Wednesday, March 8, 2017, 15:45–16:00, N 2

Time Delay in Photoionization with Light Carrying Orbital Angular Momentum — •Jonas Wätzel, Jamal Berakdar, and Carlos Granados — Institut für Physik, Martin-Luther Universität Halle-Wittenberg, Karl-Freiherr-Von-Fritsch Str. 3, 06120 Halle (Saale)

The pioneering experiment of Schultze et al. on time delay in photoemission triggered substantial experimental and theoretical activities with the aim to understand and quantitatively reproduce the results of the measurements. Up to date various mechanisms and calculation techniques were put forward.

Here we add yet a qualitatively new aspect to this topic. I will present our recent research considering an atom irradiated by a twisted light beam, also called optical vortex. Such a beam carries orbital angular momentum (OAM) which can be transferred to an electron and is controllable by the topological charge. The use of an OAM XUV laser beams to trigger photoionization implies a complete new set of optical selection rules with the consequence that the optical transitions are tuneable by the choice of the beam topological charge.

I will present the analytical and numerical results for the atomic time delay of the photoionization process of the argon 3p subshell initiated by a twisted light XUV pulse demonstrating that in different asymptotic directions either the co-rotating electron (relative to the field) or the counter rotating electron dominates photoionization amplitude. Furthermore the corresponding time delays are completely different in magnitude and sign, and depend sensitively on the position of the atom in the laser beam spot.