Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session S05: New Theoretical Methods for Pulsed Radiation-matter Interaction |
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Chair: Chris Green, Purdue University Room: Grand E |
Thursday, May 31, 2018 2:00PM - 2:30PM |
S05.00001: Strong field spectroscopy of electron dynamics: from laser filaments to strongly correlated solids Invited Speaker: Misha Ivanov Interaction of intense infrared laser light with matter, be it gases or solids, leads to rich and highly nonlinear electron dynamics. This talk will cover two very different examples. The first deals with gases, the second with strongly correlated solids. In atoms, unusual states can be created by light fields with strengths comparable to the Coulomb field that binds valence electrons in atoms. One would expect that such fields would easily set a valence electron free, perhaps within a single laser cycle. Yet, since late 1980s, theorists have speculated that atomic states become more stable when the strength of the laser field substantially exceeds the Coulomb attraction to the ionic core. The electron becomes nearly but not completely free: rapidly oscillating in the laser field, it still feels residual attraction to the core, which keeps it bound. I will describe a combination of experimental and theoretical results which show that these states arise not only in isolated atoms, but also in gases at and above atmospheric pressure, where they can act as a gain medium during laser filamentation. Using properly shaped laser pulses, gain in these states can be achieved within just a few cycles of the guided field, leading to amplified emission in the visible, at lines peculiar to the laser-dressed atom. Our work SUGGESTS that these unusual states of neutral atoms can be exploited to create a general ultrafast gain mechanism during laser filamentation. The second brings together two topics that, until very recently, have been the focus of intense but non-overlapping research efforts. The first concerns high harmonic generation in solids, which occurs when intense light field excites highly non-equilibrium electronic response in a semiconductor or a dielectric. The second concerns many-body dynamics in strongly correlated systems such as the Mott insulator. Using theorist’s model of a strongly correlated solid: the Hubbard model, we show that high harmonic generation can be used to time-resolve ultrafast many-body dynamics associated with optically driven phase transition, with accuracy far exceeding one cycle of the driving light field. These results pave the way for time-resolving highly non-equilibrium many body dynamics in strongly correlated systems, with few femtosecond accuracy. [Preview Abstract] |
Thursday, May 31, 2018 2:30PM - 3:00PM |
S05.00002: Imaging ultrafast molecular dynamics using attosecond pulses: from hydrogen to amino acids Invited Speaker: Alicia Palacios One of the most successful experimental approaches uses an ultrashort pulse in the VUV/XUV region to trigger molecular excitation or ionization, whose dynamics is then probed by the time-delayed interaction with an IR field or, ideally, with a second VUV/XUV pulse. This talk will shortly review the state-of- the- art theoretical methods that have been able to give a reliable description of ultrafast electron dynamics with sub-femtosecond resolution in recent applications using targets ranging from the hydrogen molecule to amino acids. The relevance of electron-electron and electron-nuclei correlation is explored in different scenarios. Firstly, specific applications of standard XUV/IR pump-probe protocols are explored, where the XUV ionizes the molecule into a coherent superposition of excited states of the ion and the IR field then traces the dynamics into the doubly ionized species. The evolution of the ultrafast electron dynamics is examined in two distinct scenarios: i) the dynamics triggered by single or trains of attosecond pulses in hydrogenic molecules, where the time scales of electronic and nuclear motion are comparable and ii) the dynamics launched by an attosecond pulse in amino acids, where charge migration is observed prior nuclear rearrangement. Secondly, novel approaches using single chirped VUV/XUV pulses to retrieve electron-nuclear dynamics with sub-femtosecond resolution in small target molecules are explored. The talk will conclude with a short view of the current challenges for nearly-exact theoretical simulations to describe laser-induced ultrafast processes. [Preview Abstract] |
Thursday, May 31, 2018 3:00PM - 3:30PM |
S05.00003: Method development for ultrafast correlated electron dynamics Invited Speaker: Loren Greenman Describing the correlated dynamics of electrons is a major goal of modern molecular physics. With attosecond and strong-field probes, these correlated dynamics are now being investigated on their natural timescales. These investigations are frequently understood with the aid of computational solutions of the time-dependent Schr\"odinger equation, but this is intractable for molecules larger than diatomics. Quantum chemistry can describe correlation well, but due to the localized basis functions they use it struggles to deal with the ionization that these laser pulses necessarily induce. I will describe recent developments using overset grids, which adapt to molecular geometries and describe ionization accurately and compactly. Through the use of effective orbital spaces, I will show how we can use overset grids to describe correlated electronic dynamics. [Preview Abstract] |
Thursday, May 31, 2018 3:30PM - 4:00PM |
S05.00004: Abstract Withdrawn Invited Speaker: |
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