Bulletin of the American Physical Society
Spring 2015 Joint Meeting of the Texas Section of the AAPT, Texas Section of the APS and Zone 13 of the Society of Physics Students
Volume 60, Number 2
Thursday–Saturday, March 5–7, 2015; Baytown, Texas
Session C2: Atomic, Molecular and Optical Physics, General Physics, Energy & Environment and Nanoscience |
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Chair: Heather Galloway, Texas State Unviersity - San Marcos Room: Student Center Bayer Conference Room |
Friday, March 6, 2015 2:00PM - 2:12PM |
C2.00001: A Novel Gaussian-\textit{Sinc} mixed Basis Set for Electronic Structure Calculations Jonathan Jerke, Young Lee, C.J. Tymczak A Gaussian-Sinc mixed basis set for the computation of the electronic structure atoms and molecules is presented. Excellent bases functions are known ``core'' and ``valence'' separately, such as Gaussians for the ``core'' wave and Plane-waves for ``valance'' wave functions, but as yet no is known that can accurately deal with both regimes in a single basis. A Sinc mixed basis can do both. This method resolves several issues such : i) the Sincs basis spans the same space as the plane-waves basis, yet are local enough to define all interaction elements including Exchange; ii) Gaussians span the spherically symmetric core states and can be mixed with Sinc functions in a computationally efficient methodology; iii) together, mixed basis set is a flexible, computationally efficient and a highly method for solving atomic and molecular problems. This methodology has implemented within the Hartree-Fock level of theory within ultra-strong fields. To demonstrate the utility of this new method, we calculated ground state Hartree-Fock energies to five digits accuracy in ultra strong fields for Helium to Neon, Molecular Hydrogen, Water, Carbon dioxide Benzene. [Preview Abstract] |
Friday, March 6, 2015 2:12PM - 2:24PM |
C2.00002: Improving high harmonic generation conversion efficiency M. Sayrac, A. Kolomenski, S. Anumula, Y. Boran, G. Kaya, N. Kaya, H. Schuessler High harmonic generation (HHG) can produce coherent light in the XUV spectral region. However, the conversion efficiency from IR to XUV is low. Here we present two different approaches to optimize XUV signal at moderate laser intensities of $\sim$ 1.5x10$^{14}$W/cm$^{2}$. The first approach is optimizing HHG by mixing two gases with significantly different ionization potentials (IPs), such as H$_{2}$ (15.4eV) and Ne (21.6eV). HHG in H$_{2}$ gas takes place first due to its low IP, inducing excited states and facilitating ionization and HHG in the Ne gas with high IP [1]. The second approach is to study how HHG in gases (argon, hydrogen) depends on pressure changes in the gas jet causing variations of the matching conditions and absorption [2]. To enable measurements over a wide range of pressures we employed differential pumping with an additional chamber ($\sim$ 20cm$^{3}$ volume) enclosing the gas jet. By increasing the gas jet pressure up to a maximum of $\sim$ 1.5bar for Ar, and $\sim$ 0.5bar for H$_{2}$, we observed the increase of the HHs output until the pressure in the jet reached an optimum of $\sim$ 0.2bar for Ar, and $\sim$ 0.5bar for H$_{2}$. The implementation of the additional cell enclosing the gas jet allowed to get a tenfold improvement of the HHG output. We performed modeling of the observed dependences and obtained good agreement with experimental results. [Preview Abstract] |
Friday, March 6, 2015 2:24PM - 2:36PM |
C2.00003: Spin - orbital angular momentum coupled Bose-Einstein condensate Chunlei Qu, Kuei Sun, Chuanwei Zhang The recent experimental realization of synthetic spin and linear momentum (SLM) coupling for ultracold atoms (both bosons and fermions) provides a completely new platform for exploring new quantum physics in spin-orbit coupled superfluids. Nowadays, spin-orbit coupled Bose-Einstein condensates (BEC) and degenerate Fermi gases have emerged as one of the most important frontiers of ultracold atomic physics. We pioneer the route and propose a scheme to realize another important and fundamental coupling between spin and orbital angular momentum (SOAM) in ultracold atoms using higher-order Laguerre-Gaussian laser beams. We study the ground state properties of SOAM coupled BEC in various natural geometries in experiments. We find rich phase diagrams reflecting the interplay between SOAM coupling, interaction, and external trapping. Our system, unlike the SLM coupled ones in current experiments, is naturally suited for exploring strong many-body effects with spin-orbit coupling. [Preview Abstract] |
Friday, March 6, 2015 2:36PM - 2:48PM |
C2.00004: Metastable states in the HeNe* excimer Cristian Bahrim The adiabatic electronic potential wells of the HeNe$^{\mathrm{\ast}}$ excimer include a series of vibrational states for internuclear distances R~\textless ~6 au. A set of vibrational-electronic transitions were proposed by Bahrim and Hunt [1]. The electronic potentials have been generated using a detailed model potential for the description of the Coulomb and spin-orbit interactions between Helium and Neon many-electron atoms and were tested in the analysis of atomic depolarization processes for both anisotropic and isotropic collisions. The vibrational modes within each potential well have been calculated using a Morse potential model accounting for the anharmonic motion of the atoms in collision. We propose a scheme where the HeNe$^{\mathrm{\ast}}$ excimer initially excited on a vibrational state is further excited using a short duration IR pulse on another vibrational state of a different molecular potential well. We look for an upper vibrational state with a metastable character. In our analysis we assess the influence of the avoided crossing regions between adiabatic molecular states. Our goal is to trap the HeNe$^{\mathrm{\ast}}$ excimer on long-lived (metastable) vibrational-electronic states which could be used as upper levels for new lasing transitions in IR.\\[4pt] [1] Bahrim, Cristian and Hunt, Joseph 2006 J. Phys. B: At. Mol. Opt. Phys. vol. 39, pp. 4683-4700. [Preview Abstract] |
Friday, March 6, 2015 2:48PM - 3:00PM |
C2.00005: Contrasting effects of magnetic fields on bacterial growth Martha Ariza, Samina Masood In this study we investigate the growth rates and characteristics of several bacterial strains belonging to the gram positive and gram negative groups under a variety of electromagnetic fields. Preliminary results indicate that bacterial strains respond differently to electromagnetic fields depending on their cell structure and metabolic characteristics. Gram negative bacterial strains exhibit higher growth rates under increased magnetic field while gram positive bacteria respond negatively to moderate and high electromagnetic fluxes. These findings suggest that the direction and strength of electromagnetic current influence bacterial growth and the type of response is directly related with cell type. These findings granted further investigation as magnetic field may induce a variety of responses in biological systems. [Preview Abstract] |
Friday, March 6, 2015 3:00PM - 3:12PM |
C2.00006: A Newtonian Derivation of the Equilibrium Velocity Distribution for an Ideal Gas James Woodyard, James Espinosa In the latter part of the nineteenth century, Boltzmann derived the equilibrium properties of an ideal gas by using the molecular chaos hypothesis. Some mathematicians such as Clifford Truesdell believe that the currently accepted proof of this assumption is flawed. We also believe that the application of statistical methods to this problem is resorting to nonphysical arguments that contradict the foundations of Newtonian physics. We use a modified Ritz force law to derive the equilibrium velocity distribution of an ideal gas. [Preview Abstract] |
Friday, March 6, 2015 3:12PM - 3:24PM |
C2.00007: A Ritzian Solution to Time Dilation James Espinosa, James Woodyard In 1965, Fox critically examined Walter Ritz's ballistic theory of electromagnetism after modifying this theory with the assumption that the emitter particles are absorbed after an extinction length calculated using Maxwell's equations. In his ``Evidence against Emission theories,'' he demonstrated that with this modification all of the earlier criticisms such as DeSitter's binary star argument were invalid. The time dilation of pions and the measurements of radiation from decaying particles traveling near the speed of light were definitive proof against Ritz according to Fox. Having read all of his papers in the Oeuvres with much care, we present an emission theory based on his notes that explains both of these experiments as an apparent time dilation. [Preview Abstract] |
Friday, March 6, 2015 3:24PM - 3:36PM |
C2.00008: Generalizing Cross Sections for Non-Asymptotic Measurements Jared Stenson Scattering theory is a unit of any introductory course on quantum mechanics. A major tool in scattering theory is the measurement of cross sections. Although these are exclusively defined in the asymptotic regime, they are ultimately just a normalized measurement of a dynamical system. This is especially apparent in the non-asymptotic regime of scattering. We model this time-dependent region and extract several key ideas for generalizing the cross section as a general measurement tool. This raises several interesting and fundamental issues involving interference, time-measurements, trajectory formulations of quantum mechanics, and the meaning of the so-called probability current. [Preview Abstract] |
Friday, March 6, 2015 3:36PM - 3:48PM |
C2.00009: Methods of teaching the physics of climate change in undergraduate physics courses Michael Sadler Although anthropogenic climate change is generally accepted in the scientific community, there is considerable skepticism among the general population and, therefore, in undergraduate students of all majors. Students are often asked by their peers, family members, and others, whether they ``believe'' climate change is occurring and what should be done about it (if anything). I will present my experiences and recommendations for teaching the physics of climate change to both physics and non-science majors. For non-science majors, the basic approach is to try to develop an appreciation for the scientific method (particularly peer-reviewed research) in a course on energy and the environment. For physics majors, the pertinent material is normally covered in their undergraduate courses in modern physics and thermodynamics. Nevertheless, it helps to review the basics, e.g. introductory quantum mechanics (discrete energy levels of atomic systems), molecular spectroscopy, and blackbody radiation. I have done this in a separate elective topics course, titled ``Physics of Climate Change,'' to help the students see how their knowledge gives them insight into a topic that is very volatile (socially and politically). [Preview Abstract] |
Friday, March 6, 2015 3:48PM - 4:00PM |
C2.00010: Carbon Nanotubes as Anti-Cancer Drug Delivery Agents Anvesh Bommoju, Trung Hoang, Bazlur Rashid, Paul Withey Cancer or Malignant neoplasm is the uncontrolled cell growth which is the leading cause of mortality worldwide. Carbon nanotubes (CNT) emerged as promising materials in the field of nano medicine, where they hold great importance in drug delivery, therapeutics and medical imaging. The unique properties of CNT's like size, their tubular shape and high surface area makes them a suitable tool for drug delivery purpose. In this work we have studied the effect of various concentrations of block copolymer Pluronic F127 on the dispersion of nanotubes. We examined the effect of different concentrations of polymer on different concentrations of nanotubes and selected 3 good dispersions based on the results from NIR spectroscopy. Doxorubicin hydrochloride (DOX), a potent anticancer drug was non-covalently attached to these nanotube dispersions and the cell viability was tested on HEK 293 cells. The results showed a decreased cell viability with the DOX-CNT complex compared to that of pure DOX, which indicates that nanotubes enhance cell death by carrying a high amount of drug to the cells. [Preview Abstract] |
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