Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F31: Inspirations From Experiment (E)Focus
|
Hide Abstracts |
Sponsoring Units: DCP Chair: Cristina Puzzarini Room: BCEC 203 |
Tuesday, March 5, 2019 11:15AM - 11:51AM |
F31.00001: Intrinsic Chiroptical Response: Can We Predict the Right Answer for the Right Reasons? Invited Speaker: Patrick H. Vaccaro The “intrinsic handedness” that distinguishes the mirror-image forms (enantiomers) of a chiral molecule gives rise to a variety of intriguing phenomena, perhaps none of which has had as profound and sustained an impact on the physical sciences as the characteristic interactions that take place with polarized light. Although the signatures of this optical activity have been recognized for over two centuries, their fruitful application for the determination of absolute stereochemical configuration has been revolutionized by the advent of computational paradigms capable of predicting such properties from first principles. Efforts to probe the dispersive circular birefringence (CB) of isolated chiral molecules at nonresonant wavelengths will be presented, with emphasis directed towards the marked influence that intramolecular dynamics and intermolecular forces can exert on intrinsic electronic response. Requisite isolated-molecule measurements have been made possible by ongoing development of cavity ring-down polarimetry (CRDP), an ultrasensitive chiroptical probe that has permitted the first quantitative studies of optical rotatory dispersion (ORD or wavelength-resolved CB) to be conducted in rarefied gaseous media. Quantum-chemical analyses have been enlisted to unravel the provenance of experimental findings and to elucidate the synergism among electronic and nuclear degrees of freedom that ultimately governs observed behavior. By alleviating the pronounced effects incurred from environmental perturbations (e.g., solvation), vapor-phase ORD benchmarks will be shown to afford a critical assessment of burgeoning optical-activity calculations, as well as an incisive means to expose the strengths and shortcomings inherent to various computational protocols. |
Tuesday, March 5, 2019 11:51AM - 12:27PM |
F31.00002: Probing electronic processes in large molecules Invited Speaker: Francesca Callegari Attosecond science is nowadays a well-established research field, which offers formidable tools for the investigation and control of electronic processes [1,2]. The possibility to study molecules of increasing complexity with attosecond time resolution paves the way to disclosing the role of the electron dynamics in the photo-chemistry and photo-biology of complex systems. In this context, we have recently demonstrated that attosecond pulses can initiate charge migration between different functional groups of aromatic amino-acids [3]. |
Tuesday, March 5, 2019 12:27PM - 1:03PM |
F31.00003: Designing Ligands to Control Molecular Nanomagnets: Strategies for 3d vs 4f Invited Speaker: Annie Powell NA |
Tuesday, March 5, 2019 1:03PM - 1:15PM |
F31.00004: Luminescence Measurements of the Hyperthermal Reactions of N+/N + NH3 Michael Hause, Benjamin Prince, Raymond Bemish Chemi-luminescence emitted in the ultraviolet, visible and near infrared from the collision of N+ or N with NH3 at collision energies between 20-300 eV (center of mass) was measured and the energy dependence of the respective emissions quantified in the emission excitation cross sections. For both primary collision species, the strongest features are assigned to emissions from NH (A-X) and the hydrogen Balmer series. Additional features originating from N I and NH (c-a) emissions were also observed. Most of the transitions are consistent with short-range interactions resulting in collision induced dissociation of the NH3 molecule. It has been found previously that the NH (A-X) cross sections are independent of collision partner in studies with Ar+, Kr+ and Xe+ with NH3. Reaction with N+ largely agrees with these findings, but the cross sections from collisions with neutral N is much reduced. |
Tuesday, March 5, 2019 1:15PM - 1:27PM |
F31.00005: Laser-Ionization of Energetic Compounds: Differences and Similarities between Structures and Energetics of Gaseous Monomers and Solid State Fatma AKIN As one of the processes following pulsed nanosecond or ultrafast laser ablation of solids, ionization is expected to direct molecular dissociation events. Ionization-induced effects on the RDX(s) and RDX (g) are computationally investigated using DFT methods and normal mode displacement calculations incorporating the Duschinsky effect. Structures, dissociation enthalpy and free energies of the resulting [(RDX)2]+ clusters show that ionization caused 75% of the conformers to be unstable in their neutral isomeric composition and orientation. Ionization causes charge-polarization, hydrogen-transfer, N-N dissociation and assisted HONO formation in solid RDX. The assisted HONO formation occurs via and suggests hydrogen mobility within the charged moieties, causing the greatest stabilization. The energy costs of ion-neutral dissociation are comparable to the hydrogen-transfer and NO2 loss processes. The RDX conformational identity is a determining factor in the emerging dissociation pathways in both dimeric and monomeric forms. Ionization of the RDX surface is proposed as another source of NO2 and HONO precursors of the NO+ ion observed previously. |
Tuesday, March 5, 2019 1:27PM - 1:39PM |
F31.00006: Neural network - assisted analysis of X-ray spectra of bimetallic nanoparticles Nicholas Marcella, Anatoly I Frenkel In X-ray absorption spectroscopy, it is problematic to analyze and interpret polyatomic systems consisting of elements that are neighbors in Periodic Table due to the overlapping edge regions and similar photoelectron scattering properties. This limits our ability to solve the local structure of interesting bimetallic nanocatalysts such as PtAu PdAg, IrPt, and RhAu. We have shown, recently, that X-ray absorption near edge structure (XANES) can be inverted to provide structural properties due the region's sensitivity to photoelectron scattering. Now, we take advantage of XANES sensitivity to electronic structure, specifically charge transfer. In this work, we demonstrate how our new Neural Network XANES (NN-XANES) method can be used to solve the structure of these difficult systems with better accuracy than existing methods. Our work suggests that NNs can yield distinct partial Pt-Au and Pt-Pt coordination numbers from Pt L3-edge XANES in PtAu, a feat impossible with EXAFS and other Z-contrast-limited techniques. |
Tuesday, March 5, 2019 1:39PM - 1:51PM |
F31.00007: Raman enhancement effect using 2D materials as substrates: mechanism and application Hikari Kitadai, Nannan Mao, Shengxi Huang, Xi Ling Graphene enhanced Raman scattering (GERS) was first reported in our previous work in 2010, which opened the door of using 2D materials as substrates for Raman enhancement. Here, we will present a systematic study on the Raman enhancement effect on a variety of 2D materials. Raman enhancement effect at different levels is observed on different 2D materials, which is attributed to the chemical enhancement. The degree of charge transfer between molecule and 2D materials is obtained based on the selection rule of the enhancement to vibrational modes with distinct symmetries. A strong correlation is found between the Raman enhancement effect and the degree of charge transfer. Moreover, advantages of the Raman enhancement on 2D materials for practical applications will be discussed. |
Tuesday, March 5, 2019 1:51PM - 2:03PM |
F31.00008: Probing the dynamics of small anions in optical cavities Andrea Grafton, Adam Dunkelberger, Kenan Fears, Roderick B Davidson, Blake Simpkins, Jeffrey Owrutsky Coupling vibrational modes to optical cavities offers a method to systematically and predictably modify the vibrational energy landscape of a molecule. A confined optical mode can couple to a resonant material transition and lead to enhanced absorption/emission rates, excited state population control, and the formation of new hybrid states. There is a rich history of coupling to electronic transitions, including quantum wells and J-aggregates, coupling to vibrational transitions has only been explored recently. We reported time resolved IR studies on strongly coupled vibration-cavity polaritons for W(CO)6 in hexane. The result demonstrated that much of the response is due to uncoupled reservoir excited state absorption and there is evidence for an angle-tuning dependent decay time for the upper polariton (UP) to v = 2 transition. We have explored other solutes with shorter dephasing times vibration-cavity systems. Dicyanamide and thiocyanate have strong mid-IR absorptions and are capable of strong coupling to optical fields. However, in both anions, we do not observe the UP to v = 2 transition that was observed in the W(CO)6 cavity. The results are discussed in terms of how they impact the prospects for observing polariton relaxation effects in vibration-cavity systems. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700