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Colloquium 126: Strong-field tunnelling ionization from theory to application (Yunquan Liu, Oct.09, 2013)

Colloquium 126

Title: Strong-field tunnelling ionization from theory to application

Speaker: Yunquan Liu, School of Physics, Peking University

Location: Room 111, Physics Building

Time: 15:00-16:00p, October 09th, 2013

Abstract:

Tunnelling ionization of atoms is one of the fundamental processes in strong-field physics. Since the benchmark theory developed by Keldysh, there are numerous works to investigate the strong-field tunnelling ionization. In this talk, I will present our recent experimental efforts on tunneling ionization in strong laser fields. First, we have measured photoelectron angular distributions (PADs) and observed that the yields of near-zero momentum electrons in strong-field tunneling ionization regime are much suppressed. We show that the tunneled electrons released in a certain window of initial field phases and transverse velocities are injected into the Rydberg elliptical orbits and become stabilized against ionization. Second, we have measured photoelectron angular distributions of noble gases in intense elliptically polarized laser fields, which indicate strong structure-dependent Coulomb asymmetry. We theoretically disentangle the effect of direct ionization and multiple forward scattering on Coulomb asymmetry in elliptical laser fields and quantify the roles of the ionic potential and initial transverse momentum. There is no evident initial longitudinal momentum spread at the tunnel exit according to our semiclassical simulation. At last, I will talk about the intriguing application using strong-field tunneling ionization.

Biography:

Yunquan Liu received the B.S. degree in applied physics from the Northwest Polytechnical University in 2001, and the Ph.D. degree in optical physics from the Instituteof Physics, the Chinese Academy of Sciences in 2006. From 2006 to 2009, he was a Postdoctoral Fellow at the Max Planck Institute for Nuclear Physics, Germany. In the middle of 2009, he joined Peking University through Youth Talents program. His research interests include quantum dynamics of atoms and molecules in strong laser fields.