Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F60: DCP Awards SessionFocus
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Sponsoring Units: DCP Chair: Laura Gagliardi, University of Minnesota Room: BCEC 258A |
Tuesday, March 5, 2019 11:15AM - 11:51AM |
F60.00001: Herbert P. Broida Prize Talk: Spectroscopic and dynamical probes of atmospheric reaction pathways Invited Speaker: Marsha Lester Alkene ozonolysis is a primary oxidation pathway for alkenes, the most abundant organic compounds in the Earth’s troposphere after methane, and also an important source of atmospheric hydroxyl radicals (OH). Alkene ozonolysis takes place through a complicated reaction pathway with multiple intermediates and barriers on the way to OH products. A carbonyl oxide species, known as the Criegee intermediate (RR'COO), represents a critical branching point on the pathway that controls the products formed in this important class of reactions. In this laboratory, the simplest Criegee intermediate CH2OO and methyl-, dimethyl-, ethyl-, and vinyl-substituted Criegee intermediates are generated by alternative synthetic schemes. Recent studies have focused on characterizing the Criegee intermediates utilizing infrared and ultraviolet spectroscopic methods, and examining their unimolecular and bimolecular reactions under laboratory and atmospheric conditions. Infrared ‘fingerprint’ and electronic spectra reflecting π-conjugation of the Criegee intermediates are obtained, along with time-resolved studies of their unimolecular decay to OH radical products. Remarkably, the conformation and nature of the substituents (R, R') of the Criegee intermediates are found to have a profound effect on their reaction dynamics and subsequent chemistry in the atmosphere. |
Tuesday, March 5, 2019 11:51AM - 12:27PM |
F60.00002: Irving Langmuir Prize in Chemical Physics Talk: Interphase Human Chromosome Exhibits Glassy Dynamics Invited Speaker: Dave Thirumalai The structural organization of the condensed chromosomes is being revealed using chromosome conformation capture experiments and super-resolution imaging techniques. Fingerprints of their three-dimensional organization on length scale from about hundred kilo base pairs to millions of base pairs have emerged using advances in Hi-C and super-resolution microscopy. I will describe using a minimal Chromosome Copolymer Model (CCM) with two loci types corresponding to euchromatin and heterochromatin that the dynamics is similar to that observed in glasses. Chromosome organization is hierarchical involving the formation of chromosome droplets (CDs) on short genomic scale followed by coalescence of the CDs, reminiscent of Ostwald ripening. Glassy landscapes for the condensed active chromosomes might provide a balance between genomic conformational stability and biological functions. |
Tuesday, March 5, 2019 12:27PM - 1:03PM |
F60.00003: Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics Talk: Energy transfer and conversion in molecular junctions Invited Speaker: Abraham Nitzan In molecular conductance spectroscopy, the current through a molecule (or molecules) connecting two metal or semiconductors electrodes is measured as a function of the applied voltage. With eye on potential applications, the main issues facing researchers are fabrication, characterization, stability, functionality and control. These considerations bring into focus the need to study systems comprising molecules and metal nanostructures not only for their electrical transport properties but also for their optical, thermal and mechanical response and for their function as energy conversion devices. This talk will review our work on these subjects, and present recent results on current induced light emission, photovoltaic response and electron transfer induced heat conduction in such systems. |
Tuesday, March 5, 2019 1:03PM - 1:27PM |
F60.00004: Nonadiabatic dynamics at metal surfaces: Surface hopping and electronic friction Wenjie Dou, Joseph E Subotnik The coupled electron-nuclear dynamics at molecule-metal interfaces that involve electrons transfer as well as nuclear motions are intrinsically nonadiabatic and difficult to model. Here we present two approaches to treat such nonadiabatic dynamics. In the weak molecule-metal interaction regime, we propose a surface-hopping scheme, where nuclei evolve on diabatic potential energy surfaces with stochastic hopping between them. We demonstrate that such a surface-hopping scheme gives correct detailed balance and recovers Marcus electron transfer rate at molecule-metal interfaces. In the strong molecule-metal interaction regime, we derive a Langevin equation, where classical nuclear degrees of freedom evolve on an adiabatic potential energy surface, while experiencing electronic friction and random force from electronic response. Our form of electronic friction is completely general, but does reduce to previously published expressions without electron-electron interaction. When electron-electron correlations are included, we show electronic friction exhibits Kondo resonance, whereas a mean-field treatment is completely inadequate. |
Tuesday, March 5, 2019 1:27PM - 1:51PM |
F60.00005: A molecular perspective on the structure and thermodynamics of ice interfaces in atmospherically relevant systems ARPA HUDAIT The processes at the surface of ice modulate crystal growth, adsorption of solutes and atmospherically relevant chemical reactions. These processes are not well characterized, in part, due to lack of spatial and temporal resolution of the existing experimental techniques. Despite decades of investigation, how ice interface modulate the structure of ice grown in atmospheric conditions is yet to be elucidated. In this presentation I will discuss my work using molecular simulations and theory to elucidate the role of thermodynamics of ice interfaces in modulating the structure of atmospheric ices, and the behavior of solutes at the ice interface. |
Tuesday, March 5, 2019 1:51PM - 2:15PM |
F60.00006: Cavity-Enhanced Ultrafast Spectroscopy Invited Speaker: Yuning Chen Using the general pump-probe concept, there are various spectroscopy techniques, such as transient absorption spectroscopy and 2D spectroscopy, for studying ultrafast dynamics. These methods are typically restricted to optically thick samples, such as solids and liquid solutions. In these systems, the dynamics often have broad spectral features due to the collisions between the sample molecules and the solvent molecules. |
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