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A: Fachverband Atomphysik

A 27: Visualizing Ultrafast Dynamics in atoms, molecules, and clusters

A 27.3: Hauptvortrag

Mittwoch, 20. März 2013, 15:00–15:30, E 415

Attosecond Larmor Clock for Ionization — •Olga Smirnova, Jivesh Kaushal, Ingo Barth, and Misha Ivanov — Max Born Institute, Berlin, Germany

How much time does it take to absorb a photon and remove an electron from an atom or a molecule, and how does this time depend on the number of photons required for ionization? Recent experiments suggest that it may take much less time to absorb many photons than it takes to absorb one, and that for the very large number of absorbed photons the required time tends to zero. Does it mean that, in this latter case, formation of the hole associated with electron rearrangement is instantaneous? Here we introduce a clock that resolves this paradox. We show that the spin-orbit interaction, which is the interaction of the spin of the liberated electron, or of the hole left behind, with the magnetic field created by their orbital motion, offers a built-in analogue of the famous Larmor clock for measuring time-delays during tunnelling. We calibrate the clock by first applying it to one-photon ionization and show that the time delays it measures is linked directly to the well-known Wigner-Smith time delays. We then apply the same clock to ionization in IR fields, which requires many photons. Using an example of a Krypton atom, we find delays in the hole formation and show how they depend on the number of absorbed photons. Larmor clock allows us to introduce the rigorous definition of time-delays in multi-photon ionization.