Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session U2: Hot Topics |
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Chair: David Weiss, Pennsylvania State University Room: Union ABC |
Friday, June 12, 2015 10:30AM - 11:00AM |
U2.00001: Dissociation of Peptides by Ions and Photons Invited Speaker: Sadia Bari Little is known about biological radiation action on the molecular level. The response of isolated biomolecules upon energetic photons is of great interest i.e. for astrobiology and radiobiology. Key questions concern ion chemistry in the interstellar medium, possible transport of biomolecules from space to earth and molecular mechanisms underlying biological radiation damage. Experiments with small biomolecules in the gas phase have the advantage of studying ionization and fragmentation dynamics in finite systems but are less realistic radiation damage models. To be able to investigate more complex biomolecular systems, such as peptides and proteins, we have developed a new apparatus in which a home-made electrospray source can be interfaced with a low energy (keV) ion beamline or different photon beamlines (e.g. of synchrotrons or free electron lasers). Spectra of peptides obtained with this set-up will be presented. Dependencies on energy and polarization of the radiation as well as peptide length and structure will be thereby discussed. [Preview Abstract] |
Friday, June 12, 2015 11:00AM - 11:30AM |
U2.00002: Localization in the Disordered Fermi-Hubbard Model Invited Speaker: Brian DeMarco Many-body localization (MBL) is a promising new paradigm for understanding disorder-induced localization in interacting quantum systems at non-zero temperature. We observe the emergence of an insulating state consistent with MBL in a strongly correlated atomic Fermi gas trapped in a disordered optical lattice, a closed system that realizes the disordered Fermi-Hubbard model. In measurements of disorder-induced localization obtained via mass transport, we detect three phenomena characteristic of MBL. We measure localization of this strongly interacting system at non-zero temperature, and we observe interaction-driven delocalization. We also observe localization that persists as the temperature and energy density of the gas are increased. [Preview Abstract] |
Friday, June 12, 2015 11:30AM - 12:00PM |
U2.00003: Visualizing Au-Au bond formation in solution with femtosecond X-ray scattering Invited Speaker: Shin-ichi Adachi Bond formation is an essential process in chemical reactions, but it is challenging to keep track of detailed atomic movements associated with bond formation because of its bimolecular nature. Bond formation in solution phase has been especially elusive because it is difficult to initiate and follow such diffusion-limited bimolecular processes with ultrafast time resolution. In this regard, a Au oligomer complex, [Au(CN)$^{-}_{]n}$, offers a good model system in which to study the dynamics of bond formation in solution [,2].Using femtosecond time-resolved X-ray scattering, we successfully visualized in real time the birth of a gold trimer complex, [Au(CN)$_{2}^{-}$]$_{3}$, that occurs via photoinduced formation of Au-Au covalent bonds [3]. The ground state of the trimer has Au atoms that are weakly bound to each other by aurophilic interaction and aligned in a bent geometry. Upon photoexcitation, the ground state rapidly converts into the first excited state where Au-Au covalent bonds are formed among Au atoms aligned in a linear geometry. Subsequently, the state transforms to a triplet state in 1.6 ps while accompanying further contraction of Au-Au bonds by 0.1 {\AA}. Later, the triplet state of the trimer converts to a tetramer on nanosecond time scale. This work showcases the possibility of tracking detailed structural changes in solution with sub-ps temporal and sub-angstrom spatial resolutions, thanks to the advent of X-ray free electron lasers and the advance of data analysis of time-resolved solution scattering data.\\[4pt] [1] Rawashdeh-Omary, M. A., Omary, M. A., Patterson, H. H. {\&} Fackler, J. P., J. Am. Chem. Soc. 123, 11237--11247 (2001). \\[0pt] [2] Iwamura, M., Nozaki, K., Takeuchi, S. {\&} Tahara, T., J. Am. Chem. Soc. 135, 538--541 (2013). \\[0pt] [3] Kim, K. H., Kim, J. G., Nozawa, S., Sato, T., Oang, K. Y., Kim, T. W., Ki, H., Jo, J., Park, S., Song, C., Sato, T., Ogawa, K., Togashi, T., Tono, K., Yabashi, M., Ishikawa, T., Kim, J., Ryoo, R., Kim, J., Ihee, H. {\&} Adachi, S., Nature, 518, 385-389 (2015). [Preview Abstract] |
Friday, June 12, 2015 12:00PM - 12:30PM |
U2.00004: Artificial gauge fields and chiral edge states for ultracold fermions in synthetic dimensions Invited Speaker: Leonardo Fallani I will report on very recent experiments performed at LENS with ultracold 173Yb Fermi gases in artificial gauge fields. We have engineered Raman transitions between different 173Yb nuclear spin states to synthesize an effective lattice dynamics in a finite-sized ``extra dimension,'' which is encoded in the internal degree of freedom of the atoms [1]. By using this innovative approach, we have realized synthetic magnetic fields for effectively-charged fermions in ladder geometries with a variable number of legs. Direct imaging of the individual legs allowed us to demonstrate the emergence of chiral edge currents and to observe edge-cyclotron orbits propagating along the edges of the system [2], thus providing a direct evidence of a fundamental feature of quantum Hall physics in condensed-matter systems. \\[4pt] [1] A. Celi et al., Synthetic gauge fields in synthetic dimensions, Phys. Rev. Lett. 112, 043001 (2014).\\[0pt] [2] M. Mancini et al., Observation of chiral edge states with neutral fermions in a synthetic Hall ribbon, preprint arXiv:1502.02495 (2015). [Preview Abstract] |
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