Bulletin of the American Physical Society
Spring 2017 Joint Meeting of the Texas Section of AAPT, Texas Section of APS, and Zone 13 of the Society of Physics Students
Volume 62, Number 3
Thursday–Saturday, March 9–11, 2017; San Antonio, Texas
Session F2: Atomic, Molecular and Optical Physics; Astronomy, Astrophysics and Space Science |
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Sponsoring Units: APS Chair: David Hough, Trinity University Room: Oppenheimer OC 110 |
Saturday, March 11, 2017 10:00AM - 10:12AM |
F2.00001: Nano-optical Imaging of 2D Materials Chenwei Tang, Zhe He, Dmitri Voronine Monolayer transition metal dichalcogenides (TMDC) are 2D materials with great potential in fabricating optoelectronic devices, biosensors and catalysts. Their heterostructures with nanometer-scale boundaries could be used as new platforms to improve the spatial resolution of optical imaging or as accurate sensors. Here we image molybdenum and tungsten based 2D materials and heterojuctions with a few nanometer spatial resolution using tip-enhanced photoluminescence (PL) and Kelvin probe spectroscopies. From the changes in the PL and surface potential, we determine the bandgap, defects and tip-sample interaction with nanoscale resolution. [Preview Abstract] |
Saturday, March 11, 2017 10:12AM - 10:24AM |
F2.00002: Ab Initio Study of the Barrier to Planarity of Cyclobutane, Silacyclobutane and Germacyclobutane Esther J. Ocola, Jaan Laane The structures and barriers to planarity of cyclobutane (CB), silacylobutane (SiCB) and germacyclobutane (GeCB) have been computed using MP2, CCSD, MP4(STDQ) and CCSD(T) ab initio methods and the cc-pVTZ basis set in each case. These results were compared to experimental values previously reported. The reported experimental barrier to planarity of CB ranges from 448 to 518 cm$^{\mathrm{-1}}$. The CCSD/cc-pVTZ calculation gives a value of 586 cm$^{\mathrm{-1}}$ for CB, which is in closer agreement than the other ab initio results. For SiCB the reported experimental barrier is 440 cm$^{\mathrm{-1}}$. Our calculated CCSD/cc-pVTZ barrier is 472 cm$^{\mathrm{-1}}$, in very good agreement with the experimental value, but the other methods do more poorly. The experimental value of GeCB has not been determined, but we have calculated its CCSD/cc-pVTZ value to be 409 cm$^{\mathrm{-1}}$, which we consider to be a reasonable approximation. The trend to lower barrier heights from CB to SiCB to GeCB is expected since the torsional forces involving SiH$_{\mathrm{2}}$-CH$_{\mathrm{2}}$ interactions or GeH$_{\mathrm{2}}$-CH$_{\mathrm{2\thinspace }}$interactions are less than the CH$_{\mathrm{2}}$-CH$_{\mathrm{2}}$ interactions of CB. [Preview Abstract] |
Saturday, March 11, 2017 10:24AM - 10:36AM |
F2.00003: Ring-Puckering Potential Energy Functions and Structures for Trimethylene Sulfide and Its Monovalent Cation Hye Jin Chun, Esther J. Ocola, Jaan Laane The vibrational spectra of trimethylene sulfide (TMS) and the vacuum ultraviolet mass-analyzed threshold ionization spectra of the trimethylene sulfide cation (TMS$^{\mathrm{+}})$ have been reported. Theoretical computations have been carried out to calculate the structures of both TMS and TMS$^{\mathrm{+}}$ using ab initio (MP2/cc-pVTZ) and DFT (B3LYP/cc-pVTZ) methods. These calculations were used to predict the coordinate dependent kinetic energy functions for the ring-puckering of both molecules. The kinetic energy functions were then used to calculate the refined ring-puckering potential energy functions for both species based on the previously published spectra. The refined ring-puckering potential energy functions fit the experimental data very well. TMS has an energy barrier of 271 cm$^{\mathrm{-1}}$ and energy minima at ring-puckering angles of \textpm 29 degree. TMS$^{\mathrm{+}}$ has a barrier of 60 cm$^{\mathrm{-1}}$ and the energy minima at ring-puckering angles of \textpm 21 degree. The lower barrier for TMS$^{\mathrm{+}}$ shows that the cation has lower ring angle strain than TMS itself. [Preview Abstract] |
Saturday, March 11, 2017 10:36AM - 10:48AM |
F2.00004: Constraining Dark Energy and Curvature Parameters with Observations of Supernovae, Cmb Radiation, and Baryon Acoustic Oscillations Alvaro Joseph Hu In 1998, the universe was discovered to be expanding at an accelerating rate, contrary to the assertion that its expansion was slowing down at the time. This acceleration can be accounted for by adding a $\Lambda$ term to Einstein's field equation. The common belief among cosmologists is that this $\Lambda$, or as it is also known, the cosmological constant, is associated with a dark energy component of the universe that contributes to the repulsion of the massive structures in the universe. Although current models of the universe operate under the assumption that $\Lambda$ is constant, there are some in the field that are working at determining whether or not this is in fact true. In a model with a varying dark energy, the current dark energy is given as w while the red-shift dependent dark energy is $w_a$. Using cosmological data, including Supernovae data sets PANStarrs, JLA, and Union, and pairing them with different values for the Hubble constant, we are able to achieve constraints for $w$, $w_a$, and $\Omega_k$. We use explore these dark energy models using CosmoMC for parameter fitting and CosmoEJS for visualization of the fit and expansion history of the models. [Preview Abstract] |
Saturday, March 11, 2017 10:48AM - 11:00AM |
F2.00005: The Analysis and Observational Fitting of Modified Gravity Models using \underline {CosmoEJS} Blake Palmer, Dr. Jacob Moldenhauer, Alvaro Hu The purpose of this research is to describe and attempt to understand the nature of modern cosmology through the use of modified gravity models. We present these models as alternatives to the standard Lambda CDM model. The origin, development, and growth of the universe must be accounted for in regards to a chosen theoretical cosmological model, and following recent results show the ways in which different models attempt to handle this. This project deals primarily with five different modified gravity models, those being the Einstein-DeSitter, Dvali-Gabadadze-Porrati, Modified Polytropic Cardassian, Interacting Dark Energy, and Generalized Chaplygin Gas models. These theoretical models are compared to observational data from cosmological distances on expansion history and structure growth. Also, a background and an analysis of each model is performed using new simulations built from \underline {CosmoEJS}. [Preview Abstract] |
Saturday, March 11, 2017 11:00AM - 11:12AM |
F2.00006: The case of USNO-B1.0 1219-0427833: Binary, variable or both? Mark Rodriguez, Arthur Sweeney, Richard Olenick Observations of a suspected variable star, USNO-B1.0 1219-0427833, reveal a perplexing light curve. R-band observations were made with a robotic 200 mm astrograph f/1.5 located at the University of North Texas Monroe Observatory. Over 5000 images were gathered over a five week period in July-August 2016. The extracted light curves were analyzed with differential photometry to remove possible spurious signals. Peranso was used to analyze the signals present. The star has a mean magnitude of 10.124, a B-V of 1.115, and an observed amplitude of 0.1313 with a period of 0.1652 days. The star shows several aspects of W Ursae Majoris binaries, with one or both stars pulsating. Analysis of the observations and preliminary modeling are presented. [Preview Abstract] |
Saturday, March 11, 2017 11:12AM - 11:24AM |
F2.00007: Plausible Answers to Questions Regarding Abiogenesis on Prebiotic Earth Grant Cooper Evidence indicates Earth's surface acquired necessary life-giving volatile elements - carbon, nitrogen, sulfur - from a collision with a Mercury-like planetary embryo \textasciitilde 4.4 billion y ago. Icy comets containing hydrocarbons collided with a cooling prebiotic Earth to create impact reactive environments that - via classical anthropic causality - introduced primordial ``ribozyme-like'' RNA complexes which could duplicate a few molecular units per 24 hrs. Random classical processes introduced energetically accessible duplex RNA segments containing keto - amino (-NH$_{\mathrm{2}})$ hydrogen bonds, where hydrogen bonded amino protons were subjected to quantum uncertainty limits, $\Delta $x $\Delta $p$_{\mathrm{x}} \quad \ge \quad \hbar $/2. This introduced a probability of EPR arrangement, \textit{keto-amino ¯(entanglement)}$\to $\textit{ enol}$-$\textit{imine}, where reduced energy product protons are each shared between two indistinguishable sets of \textit{intramolecular} electron lone-pairs belonging to enol oxygen and imine nitrogen on opposite genome strands. Product protons participate in entangled quantum oscillations at \textasciitilde 4\texttimes 10$^{\mathrm{13}}$ s$^{\mathrm{-1\thinspace }}$(\textasciitilde 4800$^{\mathrm{\thinspace }}$m s$^{\mathrm{-1}})$ between near symmetric energy wells in decoherence-free subspaces until measured, in a genome groove, $\delta $t \textless \textless 10$^{\mathrm{-13}}$ s, by an evolutionary selected Grover's quantum bio-processor. This quantum entanglement resource for reactive evolution provides a sequence of \textasciitilde 12 incremental entanglement-enabled improvements to genome fitness, of the form: RNA-ribozyme $\to $ RNA-protein $\to $ DNA-protein. [Preview Abstract] |
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