Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session N3: Invited Session: Ultrafast Chemical and Nanoscale DynamicsInvited
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Chair: Christoph Bostedt, Argonne National Laboratory Room: Ballroom D |
Thursday, May 26, 2016 10:30AM - 11:00AM |
N3.00001: Ultrafast electronic dynamics driven by nuclear motion. Invited Speaker: Oriol Vendrell The transfer of electrical charge on a microscopic scale plays a fundamental role in chemistry, in biology, and in technological applications. In this contribution, we will discuss situations in which nuclear motion plays a central role in driving the electronic dynamics of photo-excited or photo-ionized molecular systems. In particular, we will explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we will illustrate how the double hole can be transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. [Preview Abstract] |
Thursday, May 26, 2016 11:00AM - 11:30AM |
N3.00002: Attosecond clocking of scattering dynamics in dielectrics Invited Speaker: Matthias Kling In the past few years electronic-device scaling has progressed rapidly and miniaturization has reached physical gate lengths below 100 nm, heralding the age of nanoelectronics. Besides the effort in size scaling of integrated circuits, tremendous progress has recently been made in increasing the switching speed where strong-field-based ``dielectric-electronics'' may push it towards the petahertz frontier. In this contest, the investigation of the electronic collisional dynamics occurring in a dielectric material is of primary importance to fully understand the transport properties of such future devices. Here, we demonstrate attosecond chronoscopy of electron collisions in SiO$_{\mathrm{2}}$. In our experiment, a stream of isolated aerodynamically focused SiO$_{\mathrm{2}}$ nanoparticles of 50 nm diameter was delivered into the laser interaction region. Photoemission is initiated by an isolated 250 as pulse at 35 eV and the electron dynamics is traced by attosecond streaking using a delayed few-cycle laser pulse at 700 nm. Electrons were detected by a kilohertz, single-shot velocity-map imaging spectrometer, permitting to separate frames containing nanoparticle signals from frames containing the response of the reference gas only. We find that the nanoparticle photoemission exhibits a positive temporal shift with respect to the reference. In order to understand the physical origin of the shift we performed semi-classical Monte-Carlo trajectory simulations taking into account the near-field distributions in- and outside the nanoparticles as obtained from Mie theory. The simulations indicate a pronounced dependence of the streaking time shift near the highest measured electron energies on the inelastic scattering time, while elastic scattering only shows a small influence on the streaking time shift for typical dielectric materials. We envision our approach to provide direct time-domain access to inelastic scattering for a wide range of dielectrics. [Preview Abstract] |
Thursday, May 26, 2016 11:30AM - 12:00PM |
N3.00003: Coherent control of bond making Invited Speaker: Christiane Koch Coherent control of chemical reactions has been suggested more than 30 years ago. However, its experimental demonstration remains an open challenge until today. I will review progress toward coherent control of chemical reactions and explain why it has proven so difficult. Focussing on coherent control of bond making, I will present our recent results on femtosecond photoassociation of hot magnesium atoms [1] and its coherent control [2]. [1] L. Rybak et al., Phys. Rev. Lett. 107, 273001 (2011). [2] L. Levin et al., Phys. Rev. Lett. 114, 233003 (2015). [Preview Abstract] |
Thursday, May 26, 2016 12:00PM - 12:30PM |
N3.00004: Dynamic x-ray imaging of laser-driven nanoplasmas Invited Speaker: Thomas Fennel A major promise of current x-ray science at free electron lasers is the realization of unprecedented imaging capabilities for resolving the structure and ultrafast dynamics of matter with nanometer spatial and femtosecond temporal resolution or even below via single-shot x-ray diffraction. Laser-driven atomic clusters and nanoparticles provide an ideal platform for developing and demonstrating the required technology to extract the ultrafast transient spatiotemporal dynamics from the diffraction images. In this talk, the perspectives and challenges of dynamic x-ray imaging will be discussed using complete self-consistent microscopic electromagnetic simulations of IR pump x-ray probe imaging for the example of clusters. The results of the microscopic particle-in-cell simulations (MicPIC) enable the simulation-assisted reconstruction of corresponding experimental data. This capability is demonstrated by converting recently measured LCLS data into a ultrahigh resolution movie of laser-induced plasma expansion. Finally, routes towards reaching attosecond time resolution in the visualization of complex dynamical processes in matter by x-ray diffraction will be discussed. [Preview Abstract] |
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