Physics Commons^™

Constructing Explicit Magnetic Analogies For The Dynamics Of Glass Forming Liquids, Jacob D. Stevenson, Aleksandra M. Walczak, Randall W. Hall, Peter G. Wolynes

Randall W. Hall

By defining a spatially varying replica overlap parameter for a supercooled liquid referenced to an ensemble of fiducial liquid state configurations, we explicitly construct a constrained replica free energy functional that maps directly onto an Ising Hamiltonian with both random fields and random interactions whose statistics depend on the liquid structure. Renormalization group results for random magnets when combined with these statistics for the Lennard-Jones glass suggest that discontinuous replica symmetry breaking would occur if a liquid with short range interactions could be equilibrated at a sufficiently low temperature where its mean field configurational entropy would vanish, even though the …

Quantitative Mid-Infrared Spectra Of Allene And Propyne From Room To High Temperatures, Et. Es-Sebbar, A. Jolly, Y. Benilan, A. Farooq

Dr. Et-touhami Es-sebbar

Allene (a-C3H4; CH2CCH2) and propyne (p-C3H4; CH3C2H) have attracted much interest because of their relevance to the photochemistry in astrophysical environments as well as in combustion processes. Both allene and propyne have strong absorption in the infrared region. In the present work, infrared spectra of a-C3H4 and p-C3H4 are measured in the gas phase at temperatures ranging from 296 to 510 K. The spectra are measured over the 580–3400 cm−1 spectral region at resolutions of 0.08 and 0.25 cm−1 using Fourier Transform Infrared spectroscopy. Absolute integrated intensities of the main infrared bands are determined at room temperature and compared with …

Computational Study Of The Hydration Of Sulfuric Acid Dimers: Implications For Acid Dissociation And Aerosol Formation, Berhane Temelso, Thuong Ngoc Phan, George C. Shields

Berhane Temelso

We have investigated the thermodynamics of sulfuric acid dimer hydration using ab initio quantum mechanical methods. For (H2SO4)2(H2O)n where n = 0−6, we employed high-level ab initio calculations to locate the most stable minima for each cluster size. The results presented herein yield a detailed understanding of the first deprotonation of sulfuric acid as a function of temperature for a system consisting of two sulfuric acid molecules and up to six waters. At 0 K, a cluster of two sulfuric acid molecules and one water remains undissociated. Addition of a second water begins the deprotonation of the first sulfuric acid …

Atomistic Simulations Of The Fusion-Plasma Material Interface, Mostafa Jon Dadras

Jonny Dadras

A key issue for the successful performance of current and future fusion reactors is understanding chemical and physical processes at the Plasma Material Interface (PMI). The material surfaces may be bombarded by plasma particles in a range of impact energies (1 eV - a few keV) and kept at a range of temperatures (300 - 1000 K). The dominant processes at the PMI are reflection and retention of impacting particles and sputtering (chemical and physical). Sputtering leads to surface erosion and pollution of the plasma, both of which degrade reactor performance. Retention influences the recycling of the plasma, and in …

Absorption Cross-Section Measurements Of Methane, Ethane, Ethylene And Methanol At High Temperatures, Majed Alrefae, Et-Touhami Es-Sebbar, Aamir Farooq

Dr. Et-touhami Es-sebbar

Mid-IR absorption cross-sections are measured for methane, ethane, ethylene and methanol over 2800–3400 cm−1 (2.9–3.6 μm) spectral region. Measurements are carried out using a Fourier-Transform-Infrared (FTIR) spectrometer with temperatures ranging 296–1100 K and pressures near atmospheric. As temperature increases, the peak cross-sections decrease but the wings of the bands increase as higher rotational lines appear. Integrated band intensity is also calculated over the measured spectral region and is found to be a very weak function of temperature. The absorption cross-sections of the relatively small fuels studied here show dependence on the bath gas. This effect is investigated by studying the …

Measurements Of Linestrengths, N2-, Ar-, He- And Self-Broadening Coefficients Of Acetylene In The Ν4+Ν5 Combination Band Using A Cw Quantum Cascade Laser, Muhammad Bilal Sajid, Et-Touhami Es-Sebbar, Aamir Farooq

Dr. Et-touhami Es-sebbar

Linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene have been measured at 296 K in the P branch of the ν4+ν5 combination band for 25 rotational transitions. The effect of gas temperature is studied over 296–683 K for five transitions to allow the determination of the temperature dependent exponent n for N2- and Ar-broadening coefficients. These measurements were performed using a continuous-wave quantum cascade laser (cw-QCL) operating over 1253–1310 cm−1. Spectroscopic parameters were obtained by fitting absorption spectra using Voigt, Galatry and Rautian profiles. Linestrength and broadening results are compared with previous studies available in literature for the ν4+ν5 …

Solvent Dependency Of Azobenzene Thermal Relaxation, Chris Corkery, Alexis Goulet-Hanssens, Janet R. Belliveau, Mark Cronin-Golomb, Christopher J. Barrett

Chris Corkery

No abstract provided.

X-Ray Structure, Thermodynamics, Elastic Properties And Mdsimulations Of Cardiolipin/Dimyristoylphosphatidylcholine Mixedmembranes, Alex Boscia, Bradley Treece, Dariush Mohammadyani, Judith Klein-Seetharaman, Anthony Braun, Beate Kloesgen, Tsjerk Wassenaar, Stephanie Tristram-Nagle

Prof. Stephanie Tristram-Nagle Ph.D.

tCardiolipins (CLs) are important biologically for their unique role in biomembranes that couple phos-phorylation and electron transport like bacterial plasma membranes, chromatophores, chloroplasts andmitochondria. CLs are often tightly coupled to proteins involved in oxidative phosphorylation. The firststep in understanding the interaction of CL with proteins is to obtain the pure CL structure, and the struc-ture of mixtures of CL with other lipids. In this work we use a variety of techniques to characterize the fluidphase structure, material properties and thermodynamics of mixtures of dimyristoylphosphatidylcholine(DMPC) with tetramyristoylcardiolipin (TMCL), both with 14-carbon chains, at several mole percentages.X-ray diffuse scattering was used to …

Xena: An Automated 'Open-Source' 129xe Hyperpolarizer For Clinical Use, Panayiotis Nikolaou, Aaron M. Coffey, Laura L. Walkup, Brogan M. Gust, Nicholas Whiting, Hayley Newton, Iga Muradyan, Mikayel Dabaghyan, Kaili Ranta, Gregory D. Moroz, Matthew S. Rosen, Samuel Patz, Michael J. Barlow, Eduard Y. Chekmenev, Boyd M. Goodson

Nicholas Whiting

Standoff Methods For The Detection Of Threat Agents: A Review Of Several Promising Laser-Based Techniques, J. Bruce Johnson, Susan D. Allen, Jonathan Merten, Lewis Johnson, Daniel Pinkham, Scott Reeve

Scott Reeve

No abstract provided.

Isoprene Suppression Of New Particle Formation In A Mixed Deciduous Forest, V. P. Kanawade, B. T. Jobson, A. B. Guenther, M. E. Erupe, S. N. Pressley, S. N. Tripathi, Shan-Hu Lee

Shan-Hu Lee

Production of new particles over forests is an important source of cloud condensation nuclei that can affect climate. While such particle formation events have been widely observed, their formation mechanisms over forests are poorly understood. Our observations made in a mixed deciduous forest with large isoprene emissions during the summer displayed a surprisingly rare occurrence of new particle formation (NPF). Typically, NPF events occur around noon but no NPF events were observed during the 5 weeks of measurements. The exceptions were two evening ultrafine particle events. During the day, sulfuric acid concentrations were in the 106 cm−3 range with very …

The Effect Of Trimethylamine On Atmospheric Nucleation Involving H2so4, M. E. Erupe, A. A. Viggiano, Shan-Hu Lee

Shan-Hu Lee

Field observations and quantum chemical calculations have shown that organic amine compounds may be important for new particle formation involving H₂SO₄. Here, we report laboratory observations that investigate the effect of trimethylamine (TMA) on H₂SO₄-H₂O nucleation made under aerosol precursor concentrations typically found in the lower troposphere ([H₂SO₄] of 10⁶−10⁷ cm⁻³; [TMA] of 180–1350 pptv). The threshold [H₂SO₄] needed to produce the unity J was from 10⁶−10⁷ cm⁻³ and the slopes of Log …

New Particle Growth And Shrinkage Observed In Subtropical Environments, L. H. Young, Shan-Hu Lee, V. P. Kanawade, T-C. Hsiao, Y. L. Lee, B-F. Hwang, Y-J. Liou, H-T. Hsu, P-J. Tsai

Shan-Hu Lee

We present the first systematic analysis for new particle formation (NPF), growth and shrinkage of new particles at four different sites in subtropical central Taiwan. A total of 14 NPF events were identified from 137 days of ambient measurements during a cold and warm season. The measured formation rates of 10 nm particles (J₁₀) and growth rates were in the range of 4.4–30 cm⁻³s⁻¹ and 7.4–24 nm h⁻¹, respectively. The onset of NPF events coincided with decreases of condensation sink (CS) and increases of SO₂ under enhanced atmospheric mixing and dilution. …

Near-Unity Nuclear Polarization With An Open-Source 129xe Hyperpolarizer For Nmr And Mri, Panayiotis Nikolaou, Aaron M. Coffey, Laura L. Walkup, Brogan M. Gust, Nicholas Whiting, Hayley Newton, Scott Barcus, Iga Muradyan, Mikayel Dabaghyan, Gregory D. Moroz, Matthew S. Rosen, Samuel Patz, Michael J. Barlow, Eduard Y. Chekmenev, Boyd M. Goodson

Nicholas Whiting

Franck-Hertz Experiment, Mario Yuuji Harper, Blake Moore

Mario Yuuji Harper

The phenomenon investigated in this experiment was whether or not it was possible to excite atoms by low-energy electron bombardment, and to determine if the energy transferred from the colliding electrons were always in discrete amounts. This was investigated using thermally excited electrons that were accelerated across a potential through a homogenous gas of a single element. A slowing potential was applied at the anode making electrons that transferred their energy via inelastic collisions to lose their energy before arriving at the detector, this caused drastic decreases in the current observed. These decreases in current always occurred at the same …

Geometric-Phase Interference In A Mn12 Single-Molecule Magnet With Four-Fold Rotational Symmetry, S T. Adams, E H. Da Silva Neto, S Datta, J F. Ware, Christos Lampropoulos, G Christou, Y Myaesoedov, E Zeldov, Jonathan R. Friedman

Christos Lampropoulos

We study the magnetic relaxation rate Gamma of the single-molecule magnet Mn12-tBuAc as a function of magnetic field component HT transverse to the molecule's easy axis. When the spin is near a magnetic quantum tunneling resonance, we find that Gamma increases abruptly at certain values of HT. These increases are observed just beyond values of HT at which a geometric-phase interference effect suppresses tunneling between two excited energy levels. The effect is washed out by rotating HT away from the spin's hard axis, thereby suppressing the interference effect. Detailed numerical calculations of Gamma using the known spin Hamiltonian accurately reproduce …

Measurements Of Nh3 Linestrengths And Collisional Broadening Coefficients In N2, O2, Co2, And H2o Near 1103.46 Cm−1, Kyle Owen, Et-Touhami Es-Sebbar, Aamir Farooq

Dr. Et-touhami Es-sebbar

Laser-based ammonia gas sensors have useful applications in many fields including combustion, atmospheric monitoring, and medical diagnostics. Calibration-free trace gas sensors require the spectroscopic parameters including linestrengths and collisional broadening coefficients to be known. Ammonia's strong ν2 vibrational band between View the MathML source has the high absorption strength needed for sensing small concentrations. Within this band, the 1103.46 cm−1 feature is one of the strongest and has minimal interference from CO2 and H2O. However, the six rotational transitions that make up this feature have not been studied previously with absorption spectroscopy due to their small line spacing ranging from …

Effects Of N2o And O2 Addition To Nitrogen Townsend Dielectric Barrier Discharges At Atmospheric Pressure On The Absolute Ground-State Atomic Nitrogen Density, Et. Es-Sebbar, N. Gherardi, F. Massines

Dr. Et-touhami Es-sebbar

Absolute ground-state density of nitrogen atoms N (2p3 4S3/2) in non-equilibrium Townsend dielectric barrier discharges (TDBDs) at atmospheric pressure sustained in N2/N2O and N2/O2 gas mixtures has been measured using Two-photon absorption laser-induced fluorescence (TALIF) spectroscopy. The quantitative measurements have been obtained by TALIF calibration using krypton as a reference gas. We previously reported that the maximum of N (2p3 4S3/2) atom density is around 3 × 1014 cm−3 in pure nitrogen TDBD, and that this maximum depends strongly on the mean energy dissipated in the gas. In the two gas mixtures studied here, results show that the absolute N …

Determination Of Kinetic Parameters From The Thermogravimetric Data Set Of Biomass Samples, Karol Postawa, Wojciech M. Budzianowski

Wojciech Budzianowski

This article describes methods of the determination of kinetic parameters from the thermogravimetric data set of biomass samples. It presents the methodology of the research, description of the needed equipment, and the method of analysis of thermogravimetric data. It describes both methodology of obtaining quantitative data such as kinetic parameters as well as of obtaining qualitative data like the composition of biomass. The study is focused mainly on plant biomass because it is easy in harvesting and preparation. Methodology is shown on the sample containing corn stover which is subsequently pyrolysed. The investigated sample show the kinetic of first order …

Temperature-Dependent Absorption Cross-Section Measurements Of 1-Butene (1-C4h8) In Vuv And Ir, Et-Touhami Es-Sebbar, Yves Benilan, Aamir Farooq

Dr. Et-touhami Es-sebbar

Vacuum ultraviolet (VUV) and infrared (IR) absorption cross-section measurements of 1-butene (1-C4H8; CH2=CHCH2CH3; Butylene) are reported over the temperature range of 296–529 K. The VUV measurements are performed between 115 and 205 nm using synchrotron radiation as a tunable VUV light source. Fourier Transform Infrared (FTIR) spectroscopy is employed to measure absorption cross-section and band strengths in the IR region between 1.54 and 25 μm (∼6500–400 cm−1). The measured room-temperature VUV and IR absorption cross-sections are compared with available literature data and are found to be in good agreement. The oscillator strength for the electronic transition (A1A′→X1A′) around 150–205 nm …

Double Layer In Ionic Liquids: Overscreening Versus Crowding, Martin Z. Bazant, Brian D. Storey, Alexei A. Kornyshev

Brian Storey

We develop a simple Landau-Ginzburg-type continuum theory of solvent-free ionic liquids and use it to predict the structure of the electrical double layer. The model captures overscreening from short-range correlations, dominant at small voltages, and steric constraints of finite ion sizes, which prevail at large voltages. Increasing the voltage gradually suppresses overscreening in favor of the crowding of counterions in a condensed inner layer near the electrode. This prediction, the ion profiles, and the capacitance-voltage dependence are consistent with recent computer simulations and experiments on room-temperature ionic liquids, using a correlation length of order the ion size.

Mixture Segregation Within Sonoluminescence Bubbles, Brian D. Storey, Andrew J. Szeri

Brian Storey

This paper concerns a relaxation of the assumption of uniform mixture composition in the interior of sonoluminescence bubbles. Intense temperature and pressure gradients within the bubble drive relative mass diffusion which overwhelms diffusion driven by concentration gradients. This thermal and pressure diffusion results in a robust compositional inhomogeneity in the bubble which lasts several orders of magnitude longer than the temperature peak or light pulse at the main collapse of the bubble. This effect has important consequences for control of sonoluminescence, gas dynamics, sonochemistry, and the physics of light production.

Capacitively Coupled Radio-Frequency Discharges In Nitrogen At Low Pressures, L. L Alves, L. Marques, C. D Pintassilgo, W. Wattieaux, Et. Es-Sebbar, J. Berndt, E. Kovačević, N. Carrasco, L. Boufendi, G. Cernogora

Dr. Et-touhami Es-sebbar

This paper uses experiments and modelling to study capacitively coupled radio-frequency (rf) discharges in pure nitrogen, at 13.56 MHz frequency, 0.1–1 mbar pressures and 2–30 W coupled powers. Experiments performed on two similar (not twin) setups, existing in the LATMOS and the GREMI laboratories, include electrical and optical emission spectroscopy (OES) measurements. Electrical measurements give the rf-applied and the direct-current-self-bias voltages, the effective power coupled to the plasma and the average electron density. OES diagnostics measure the intensities of radiative transitions with the nitrogen second-positive and first-negative systems, and with the 811.5 nm atomic line of argon (present as an …

Ionization Photophysics And Rydberg Spectroscopy Of Diacetylene, M. Schwell, Y. Benilan, N.. Fray, M.-C. Gazeau, Et. Es-Sebbar, F.-G. Levrel, N. Campion, S. Leach

Dr. Et-touhami Es-sebbar

Photoionization of diacetylene was studied using synchrotron radiation over the range 8–24 eV, with photoelectron-photoion coincidence (PEPICO) and threshold photoelectron–photoion coincidence (TPEPICO) techniques. Mass spectra, ion yields, total and partial ionization cross-sections were measured. The adiabatic ionization energy of diacetylene was determined as IEad = (10.17 ± 0.01) eV, and the appearance energy of the principal fragment ion C4H+ as AE = (16.15 ± 0.03) eV. Calculated appearance energies of other fragment ions were used to infer aspects of dissociation pathways forming the weaker fragment ions , C3H+, and C2H+. Structured autoionization features observed in the PEPICO spectrum of diacetylene …

Volatile Products Controlling Titan’S Tholins Production, N. Carrasco, T. Gautier, Et. Es-Sebbar, P. Pernot, G. Cernogora

Dr. Et-touhami Es-sebbar

A quantitative agreement between nitrile relative abundances and Titan’s atmospheric composition was recently shown with a reactor simulating the global chemistry occurring in Titan’s atmosphere [Gautier et al. (2011) Icarus, 213: 625]. Here we present a complementary study on the same reactor using an in-situ diagnostic of the gas phase composition. Various initial N2-CH4 gas mixtures (methane varying from 1 to 10%) are studied, with a monitoring of the methane consumption and of the stable gas neutrals by in-situ mass spectrometry. Atomic hydrogen is also measured by optical emission spectroscopy. A positive correlation is found between atomic hydrogen abundance and …

Vuv Photoionization Of Acetamide Studied By Electron / Ion Coincidence Spectroscopy In The 8-24 Ev Photon Energy Range, M. Schwell, Y. Bénilan, N. Fray, M.-C Gazeau, Et. Es-Sebbar, Gustavo A. Garcia, L. Nahon, N. Champion, S. Leach

Dr. Et-touhami Es-sebbar

A VUV photoionization study of acetamide was carried out over the 8-24 eV photon energy range using synchrotron radiation and photoelectron/photoion coincidence (PEPICO) spectroscopy. Threshold photoelectron photoion coincidence (TPEPICO) measurements were also made. Photoion yield curves and branching ratios were measured for the parent ion and six fragment ions. The adiabatic ionization energy of acetamide was determined as I.E (12A’) = (9.71±0.02) eV, in agreement with an earlier reported photoionization mass spectrometry (PIMS) value. The adiabatic energy of the first excited state of the ion, 12A”, was determined to be ≈ 10.1 eV. Assignments of the fragment ions and the …

Hydrogen Production From Biogas By Oxy-Reforming: Reaction System Analysis, Aleksandra Terlecka, Wojciech M. Budzianowski

Wojciech Budzianowski

Oxy-reforming is emerging as an interesting alternative to conventional methods of hydrogen generation. The current article characterises this process through analysis of individual reactions: SMR (steam methane reforming), WGS (water gas shift) and CPO (catalytic partial oxidation). Analyses relate to optimisation of thermal conditions thus enabling cost-effectivenes of the process.

Using Frequency-Narrowed, Tunable Laser Diode Arrays With Integrated Volume Holographic Gratings For Spin-Exchange Optical Pumping At High Resonant Fluxes And Xenon Densities, Nicholas Whiting, Panayiotis Nikolaou, Neil A. Eschmann, Michael J. Barlow, R Lammert, J Ungar, W Hu, Laurent Vaissie, Boyd M. Goodson

Nicholas Whiting

Cavity Ringdown Spectroscopy Of 13c2h2 In The 12900-13400 Region.Pdf, Christopher J. Lue, Michael Sullivan, Mark Draganjac, Scott Reeve

Scott Reeve

No abstract provided.

Vuv Absorption Cross Section Of Benzene, Relevance For Titan’S Atmosphere, F-J. Capalbo, Y. Bénilan, N. Fray, M. Schwell, Et. Es-Sebbar, N. Champion, T. Koskinen, R. Yelle

Dr. Et-touhami Es-sebbar

Saturn's largest satellite, Titan, is the only one in the Solar System known to have a thick N2/CH4, planet like atmosphere. The dissociation of these principal components and the recombination of the products make this atmosphere to be rich in organic compounds of high interest for astrobiology. Solar and stellar occultations observed by the Ultraviolet Imaging Spectrograph (UVIS) on board the Cassini spacecraft can be used to characterize the composition of Titan’s upper atmosphere (400 – 1400 km). The results depend strongly on the knowledge of the molecular absorption cross sections of the atmospheric constituents (Ferradaz et al. 2009). This …