Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session Y35: Materials |
Hide Abstracts |
Sponsoring Units: DCP Chair: Mark Ratner, Northwestern University Room: LACC 511B |
Friday, March 25, 2005 11:15AM - 11:27AM |
Y35.00001: Polymeric CO: A new class of High Energy Density Material Magnus Lipp, William Evans, Hyunchae Cynn, Bruce Baer, Ken Visbeck, Choong-Shik Yoo Covalently bonded extended phases of molecular solids made of first- and second-row elements at high pressures are a new class of material with advanced optical, mechanical and energetic properties. The existence of such extended solids has recently been demonstrated using diamond anvil cells in several systems, including N2, CO2, and CO. However, the microscopic quantities produced at the formidable high-pressure/temperature conditions have limited the characterization of their predicted novel properties including high-energy content. Here we present the first experimental evidence that these extended low-Z solids are indeed high energy density materials via milligram-scale high-pressure synthesis, recovery and characterization of polymeric CO (p-CO).~ This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. [Preview Abstract] |
Friday, March 25, 2005 11:27AM - 11:39AM |
Y35.00002: Identification of intrinsic and extrinsic transitions in pentacene single crystals by optical methods (*) Rui He, X. Chi, Aron Pinczuk, D.V. Lang, A.P. Ramirez Pentacene single crystals with different purity levels are studied by using photoluminescence and resonant Raman scattering. Two luminescence bands are identified as intrinsic optical emissions by recombination of free excitons and self- trapped excitons. The luminescence bands observed below 1.6eV are attributed to the extrinsic optical emissions. Raman scattering from the pentacene crystals exhibits resonance enhancements with the two intrinsic bands. Temperature dependence of the luminescence from the pentacene crystals reveals that optical emission from the self-trapped excitons are sensitive to the sample qualities between 50 and 100K, and its intensity can be quenched by extrinsic traps. \newline \newline (*) Supported primarily by the Nanoscale Science and Engineering Initiative of the NSF under NSF Award Number CHE-0117752 and by the NYSTAR, and by a research grant of the W. M. Keck Foundation. We thank Mark Hybertsen, I. Dujovne, and C. F. Hirjibehedin for their helpful discussions. [Preview Abstract] |
Friday, March 25, 2005 11:39AM - 11:51AM |
Y35.00003: Photophysical properties of hemicyanine dyes in zeolite film grown on glass plate Doseok Kim, T. K. Shim, M. H. Lee, H. S. Kim, K. B. Yoon Hemicyanine dye molecules were put into the pores of zeolite (ZSM-5) crystals self-assembled on a glass substrate, and their photophysical properties were investigated by using time-- resolved fluorescence methods. The dye molecules were found to be aligned normal to the plate along the vertical channel of the pore and oriented unidirectionally. The photoluminescence (PL) decay lifetime of the dye molecules in zeolite pore measured by the Time-Correlated Single Photon Counting (TCSPC) method was several nanoseconds, which is much longer compared to that of the same dye in solution phase. This can be interpreted as the restricted twisted intramolecular charge transfer of the molecules confined in zeolite pores. We compared the photophysical properties (steady-state and time- resolved PL) from the molecules in various zeolite crystals with different structural and dielectric properties. This zeolite film can potentially be used as a matrix for investigating the optical and photophysical properties of a molecule in controlled environment. [Preview Abstract] |
Friday, March 25, 2005 11:51AM - 12:03PM |
Y35.00004: Mass Spectrometric Analyses of Two Isomeric Forms of Functionalized Pentacene Molecules Svitlana Shcherbyna, Diethard Bohme, Vladimir Baranov, John Anthony Functionalized Pentacene (FP) derivatives are one of the most interesting semiconducting organic materials for use in molecular electronics. We report a comprehensive Mass Spectrometic (MS) study of two isomeric forms of FP molecules that have recently gained considerable attention due to their high charge carrier mobility in organic thin film transistors (OTFT). Both compounds were investigated in an Electrospray Ion Source Triple Quadruple Mass Spectrometer (ESI-MS) fitted with an Ion-Molecule Reactor instead of a Collision Cell. Attempts were made to distinguish the symmetric and asymmetric isomers of FP employing differences in the rates of ion-molecule reactions, ion mobilities and Collisional Induced Dissociation (CID) patterns. In addition, the Matrix-Assisted Laser Desorption/Ionization technique (MALDI-MS) and Ion Mobility Spectrometry (IMS) were employed to study different ionization and ion transport methods prior to mass separation. IMS was able to separate the isomers only marginally. Strong ion-molecule association was observed during MALDI ionization, particularly for the symmetric FP isomer, under the reduced pressure of the source. The results of these measurements and their interpretation will be presented. [Preview Abstract] |
Friday, March 25, 2005 12:03PM - 12:15PM |
Y35.00005: Mass Transport and the Ion Beam Sculpting of Solid State Nano-scale pores Toshiyuki Mitsui, Derek Stein, Jene Golovchenko We report on AFM and TEM studies of mass transport during the formation of isolated nano-scale pores formed in silicon nitride membranes with the aid of surface ion beam exposure.~This ion beam sculpting process allows the fabrication of nanopores with nanometer scale control for use in single molecule detection experiments. The nano-scale pores generally close under ion beam exposure and we show from AFM studies that excess material is transported to the vicinity of the pore position and accumulates over regions surrounding the pore that extend hundreds of nanometers from it.~TEM images of multiple pore arrays formed by Ion Beam Sculpting indicate proximity effects associated with the surface diffusion and membrane stress effects leading to pore formation. In addition we discuss the dramatic role of accumulated surface charge during ion beam exposure on surface atomic transport in the formation of these nano-scale pore structures. [Preview Abstract] |
Friday, March 25, 2005 12:15PM - 12:27PM |
Y35.00006: Neutron and Thermodynamic Investigation of n-Butane Adsorption on MgO(100) Surfaces Sami Chanaa, Rick Cook, Tom Arnold, T. Ramirez-Cuesta, S. Clarke, John Larese The adsorption properties of thin films normal butane films adsorbed on the MgO (100) surface were investigated using neutron scattering and volumetric isotherm techniques. A series of high-resolution, adsorption isotherm measurements were performed between 145K and 200K using an automated volumetric adsorption apparatus. These data were used to determine both the two-dimensional isothermal compressibility and the isosteric heat of adsorption and to identify regions where phase transitions might occur. Evidence is found for the presence of two layering transitions. Using neutron diffraction. We find that at low temperatures monolayer butane forms a commensurate solid phase that is commensurate with the underlying MgO (100) surface. Inelastic neutron spectroscopy was used to gain some preliminary indications of the dynamical response of the butane solid phase. Comparisons of the neutron spectra with calculations of the molecular-vibrational modes will be made. [Preview Abstract] |
Friday, March 25, 2005 12:27PM - 12:39PM |
Y35.00007: Scattering-type near-field infrared microscopy of selforganized nanodomains of diblock copolymers Markus B. Raschke, Leopoldo Molina, Dong Ha Kim, Wolfgang Knoll, Karsten Hinrichs The expansion of scattering-type scanning near-field optical microscopy ({\em s}-SNOM) into the infrared spectral region provides the ability to achieve all-optical resolution down to the several nanometer range in combination with the chemical sensitivity of infrared spectroscopy. Here, we have performed a nanometer scale surface analysis and identification of domains formed by phase separation of the diblock copolymers polystyrene-{\em b}-polyvinylpyridine (PS-b-P2VP) and polystyrene-{\em b}-polyethyleneoxide (PS-b-PEO). This has been achieved by means of non-interferometric IR-scattering detection based on epi-illumination of sharp Au-coated cantilever tips in a noncontact atomic force microscopy configuration. Contrast is obtained probing characteristic differences in the C--H stretch vibrational resonances between the different polymer constituents and a spatial resolution down to 10 nm has been made possible. The mechanism of the near-field tip-sample coupling by vibrational resonances responsible for the imaging contrast has been deduced and can be modelled based on the dielectric functions of the polymer compounds measured by spectroscopic ellipsometry. [Preview Abstract] |
Friday, March 25, 2005 12:39PM - 12:51PM |
Y35.00008: Quantum-mechanical process in the gas-surface reaction and PESs Taizo Sasaki The reaction between a surface and a molecule is investigated by using the one-dimensional model potential-energy surfaces (PESs) with multi components, which represents the electron transfer effect. The motion of the molecule is treated quantum mechanically, and the sticking probabilities are calculated for various types of the PES model. For the O$_2$-Al(111) reaction, the initial sticking probability ($S_0$) with the S-shape has been found experimentally[1]. The present study exhibits that such a behavior can be seen only in the case with a small electron-transfer matrix and a slowly-varying potential. On the basis of the results, it is concluded that $S_0$ in the observed reaction should be attributed not to the diabatic effect, but to the tunneling through the energy barrier which appears in the adiabatic approximation to PES.¥¥ [1] L. \"{O}sterlund, I. Zor\'{i}c, and B. Kasemo, Phys. Rev. B \textbf{55}, 15452 (1997). [Preview Abstract] |
Friday, March 25, 2005 12:51PM - 1:03PM |
Y35.00009: Study of Binding Energies of Halogen Molecules in Solid State M.M. Aryal, D.R. Mishra, D.D. Paudyal, S. Byahut, N.B. Maharjan, R.H. Scheicher, Junho Jeong, T.P. Das As part of a program for first-principles understanding of the binding of molecules in molecular solids, we have investigated the binding energies of the halogen molecules in chlorine, bromine and iodine. For studying the electronic structures of these solid-state systems, we have employed the Hartree-Fock Cluster Procedure together with Many-Body Perturbation Theory, the latter allowing direct inclusion of Van der Waals interactions between the molecules which are found to be crucial for the stability of these molecular solids since one-electron effects in the intermolecular interactions are found to be repulsive, opposing the binding of these molecules. The VDW effect is seen to increase systematically from Cl to I, as expected form polarizability considerations. [Preview Abstract] |
Friday, March 25, 2005 1:03PM - 1:15PM |
Y35.00010: High-Field Transient Electron Paramagnetic Resonance of Excited Triplet States M. Bortolus, J. van Tol, M. Prato, A.-L. Maniero The zero-field splitting of the excited triplet states of organic molecules often is of the order of 1 GHz or less, and transient EPR at X-band is generally sufficient for the determination of the zero-field splitting and kinetic parameters in these type of molecules. However, information on the g-factor and g-anisotropy cannot be obtained at conventional EPR frequencies, and interpretations of the data in terms of electronic structure are mostly limited to symmetry considerations. On the other hand information of the g-anisotropy provides additional clues with respect to electronic structure, while a direct comparison with radical-ion forms of the molecules becomes possible. Experimental data of transient EPR at 240 GHz will be presented for a variety of methano-fullerenes and pyrrolidino-fullerenes, either embedded in a polymer of in partially oriented liquid crystals. It will be shown that transient EPR at these very high frequencies can accurately determine the g-anisotropy and in some cases the orientation of the g-tensor with respect to the ZFS tensor. The information gained will be discussed in relation to the electronic structure of the lowest excited triplet state of these molecules. [Preview Abstract] |
Friday, March 25, 2005 1:15PM - 1:27PM |
Y35.00011: Measurement of the Born-Oppenheimer Potential in a Superprotonic Conductor Using Deep Inelastic Neutron Scattering George Reiter, Dirar Homouz, Juergen Eckert, Robert Blinc, Phil Platzman The momentum distribution of the proton in the superionic conductor Rb3H(SO4)2 is measured using Deep Inelastic Neutron Scattering with the Vesuvio Instrument at ISIS.This material is well suited to a single particle interpretation of the momentum distribution, and the results have been used to extract a direct measurement of the full 3-D Born-Oppenheimer potential surface at 10K, 70K and 102K. We find that there is significant variation of the potential surface in the direction of the bond as the temperature is varied, with the proton becoming more confined in this direction at higher temperatures [Preview Abstract] |
Friday, March 25, 2005 1:27PM - 1:39PM |
Y35.00012: Interaction of oxygen with oxide-supported gold films Su Ying Quek, Joydeep Bhattacharjee, Umesh Waghmare, Efthimios Kaxiras Whilst bulk gold is known to be inert, oxide-supported gold nanoparticles have been found to be highly effective in the catalysis of low temperature oxidation of carbon monoxide. This remarkable activity has been attributed to effects of charge transfer to and from the gold nanoparticles, quantum size effects, reduced co-ordination of gold atoms, as well as interface effects. However, the relative importance of such effects is still controversial. In this work, we seek to distinguish these effects and understand their relative importance, using model systems involving oxide-supported gold films. [Preview Abstract] |
Friday, March 25, 2005 1:39PM - 1:51PM |
Y35.00013: Pulse chirping in coherent control via stimulated Raman scattering Svetlana Malinovskaya Selective excitation of molecular vibrations with implementation of ultrashort chirped laser pulses is considered in stimulated Raman spectroscopy. An effective control is demonstrated via adiabatic pulse interaction with molecules. A model of two, two-level systems interacting with transform-limited pump and chirped Stokes pulse is used. The goal of creating a desired coherent superposition of states is analyzed within a dressed state picture. [Preview Abstract] |
|
Y35.00014: Fluorescence dynamics of microsphere-adsorbed sunscreens R. Krishnan, T. Nordlund Sunscreens are generally oily substances which are prepared in organic solvents, emulsions or dispersions with micro- or nanoparticles. These molecules adsorb to and integrate into skin cells. In order to understand the photophysical properties of the sunscreen, we compare steady-state and time-resolved fluorescence in organic solvent of varying dielectric constant $\varepsilon $ and adsorbed to polystyrene microspheres and dispersed in water. Steady-state fluorescence is highest and average fluorescence lifetime longest in toluene, the solvent of lowest $\varepsilon $. However, there is no uniform dependence on $\varepsilon $. Sunscreens PABA and padimate-O show complex emission spectra. Microsphere-adsorbed sunscreens exhibit highly non-exponential decay, illustrative of multiple environments of the adsorbed molecule. The heterogeneous fluorescence dynamics likely characterizes sunscreen adsorbed to cells. [Preview Abstract] |
|
Y35.00015: Cyclodextrin-templated Fluorescent Anisotropic Structure Jong Seung Park, James N. Wilson, Uwe H.F. Bunz, Mohan Srinivasarao $\gamma -$Cyclodextrin ($\gamma $-CD) consisting of eight glucose units has a large cavity with diameters of 9.5 {\AA}. This large cavity size allows the inclusion of molecules and the proximity of the molecules can lead to electronic interaction among them. In this presentation, we describe the complex formation of linear and planar molecule acetylene dye with $\gamma $-CD. When mixed with $\gamma $-CD in high enough concentrations, the dye with CD forms a liquid that is anisotropic in nature, as evidenced by observations using a polarized light microscope. Fluorescent properties of these complexes were examined to probe the nature of the complex formed in aqueous solutions. Wide angle X-ray scattering (WAXD) and differential scanning calorimetry (DSC) were also used to characterize the complex formed. [Preview Abstract] |
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