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Physics

Spectroscopy

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Displaying 651 - 675 of 948

Time-Resolved Infrared Spectroscopy of an [FeFe]-Hydrogenase Model Compound

March 26, 2012
Author(s)
Edwin J. Heilweil
Naturally occurring hydrogenases catalyze the reaction of H+ to form H2 gas. To develop a hydrogen source that is not reliant on fossil fuels, synthetic [FeFe]-hydrogenase model species are being studied. These compounds have a wing-like structure with a

In Situ Raman Monitoring of Ring-Opening Copolymerizations

March 25, 2012
Author(s)
Matthew T. Hunley, Santanu S. Kundu, Peter M. Johnson, Kathryn Beers
Recent advances in enzyme, metal, and organic catalysts have enabled the development of advanced functional polymers from cyclic ester and cyclic carbonate monomers. In this work, we present an in situ technique to monitor ring-opening polymerization using

Environmental Metabolomics

March 15, 2012
Author(s)
Daniel W. Bearden
The application of metabolomics in the field of environmental science or ecology, which has developed based substantially on NMR spectroscopic approaches, is a fast paced, rapidly developing field which seems to be poised to help re-frame the discussion of

Direct-comb molecular spectroscopy with accurate, resolved comb teeth over 43 THz

February 15, 2012
Author(s)
Alexander M. Zolot, Fabrizio R. Giorgetta, Esther Baumann, Jeffrey W. Nicholson, William C. Swann, Ian R. Coddington, Nathan R. Newbury
We demonstrate a dual comb spectrometer using stabilized frequency combs spanning 176 THz to 219 THz (1370 nm to 1700 nm) in the near infrared. Measurements of amplitude and phase response at each individual comb tooth span the full 43 THz, generating ~430

Penning traps with unitary architecture for storage of highly charged ions

February 15, 2012
Author(s)
Joseph N. Tan, Samuel M. Brewer, Nicholas D. Guise
Penning traps are made extremely compact by embedding rare-earth permanent magnets in the electrode structure. Axially-oriented NdFeB magnets are used to produce 0.32 T for ion trapping in unitary architectures that functionally couple the electric and

High-resolution, high-accuracy dual comb spectroscopy with over 40 THz bandwidth

January 20, 2012
Author(s)
Alexander M. Zolot, Fabrizio R. Giorgetta, Esther Baumann, William C. Swann, Jeff Nicholson, Ian R. Coddington, Nathan R. Newbury
Most spectroscopic instruments directly measure optical wavelength, which is converted to frequency and calibrated against spectral features that have traditionally been measured using complicated frequency chain methods. In the past decade optical

First high-resolution analysis of the nu15, nu12, nu5, nu10 and nu2 bands of oxirane

January 15, 2012
Author(s)
Walter J. Lafferty, Jean-Marie Flaud, F. Kwabia Tchana, A. Perrin
Fourier transform spectra of Oxirane (ethylene oxide, c-C2H4O) have been recorded in the 730 cm-1 to 1560 cm-1 (6.4 to 13.7 µm) spectral region using a Bruker IFS125HR spectrometer at a resolution of 0.0019 cm-1. A total of six vibration bands, ν15, ν12

Predictive Gold Nanocluster Formation Controlled by Metal-Ligand Complexes

January 9, 2012
Author(s)
John M. Pettibone, Jeffrey W. Hudgens
The formation of ligand-protected transition metal nanoclusters in size-selective syntheses is driven by the inherent properties of the protecting ligands. We have previously reported the selective, monodisperse product formation of phosphine protected Au

2-Bromo-3,3,3-Trifluoropropene: OH Reaction Rate Constant, IR Absorption Spectrum, Ozone Depletion Potentials and Global Warming Potentials

December 30, 2011
Author(s)
Kenneth O. Patten, Victor Khamaganov, Vladimir L. Orkin, Steven L. Baughcum, Donald J. Wuebbles
The rate constant for the gas phase reaction of OH radicals with BTP (2-Bromo-3,3,3-trifluoropropene, CH2=CBrCF3) was measured using a flash photolysis resonance-fluorescence technique over the temperature range 220 K to 370 K. The Arrhenius plot was found

Spectroscopy of the methane N3 Band with an accurate midinfrared coherent dual-comb spectrometer

December 28, 2011
Author(s)
Esther Baumann, Fabrizio R. Giorgetta, William C. Swann, Alexander M. Zolot, Ian R. Coddington, Nathan R. Newbury
We demonstrate a high-accuracy dual-comb spectrometer centered at 3.4 υm. The amplitude and phase spectra of the P,, Q, and partial R branches of the methane Ņ3 band are measured at 25 to 100 MHz point spacing with resolution under 10 kHz and a signal-to

A Large-Signal Model of Ferroelectric Thin-Film Transmission Lines"

December 1, 2011
Author(s)
Eduard Rocas, Juan C. Collado Gomez, Jordi Mateu, Nate Orloff, James Booth, Juan M. O'C allaghan
"This work evaluates the microwave nonlinear properties and tuning at RF frequencies of ferroelectric Ba0.3Sr0.7TiO3 thin-films by on-wafer measurements of the second and third-order harmonics and intermodulation products of several coplanar transmission

Capacitive readout technique for studies of dissipation in GaN nanowire mechanical resonators

November 11, 2011
Author(s)
Kristine A. Bertness, Joshua R. Montague, Norman A. Sanford, Victor Bright, Charles T. Rogers
A variable-temperature, homodyne reflectometry measurement technique for detecting nanoscale mechanical motion has recently been developed. We have extended this technique to make the first all-electrical measurements of an ensemble of as-grown, c-axis

Characterization of (1-3,1-6)-b-D-Glucan Side Chain Structure Provides the Basis for a New Model of Fungal Cell Wall Rigidity and Flexibility

November 11, 2011
Author(s)
Daniel W. Bearden, Douglas W. Lowman, Lara J. West, Michael F. Wempe, Trevor D. Power, Harry E. Ensley, Ken Haynes, David L. Williams, Michael D. Kruppa
Glucan is a (1-3)-β-linked glucose polymer with (1-6)-β-linked side chains and a major component of fungal cell walls. Glucans provide structural integrity to the fungal cell wall. The nature of the (1-6)-β-linked side chain structure of fungal (1-3,1-6)-β

In situ monitoring of enzyme-catalyzed (co)polymerizations by Raman spectroscopy

November 10, 2011
Author(s)
Matthew T. Hunley, Atul Bhangale, Santanu S. Kundu, Peter M. Johnson, Michael S. Waters, Richard Gross, Kathryn Beers
In situ, fiber optic-based Raman spectroscopy provided real time monitoring of enzyme-catalyzed ring-opening homo- and copolymerizations of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL). A custom designed reactor equipped with in situ fiber optic probe
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