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Displaying 1051 - 1075 of 2028

Violation of the Condon Approximation in Semiconducting Carbon Nanotubes

June 28, 2011
Author(s)
Ming Zheng
A long-held but untested fundamental assumption in Raman spectroscopy of carbon nanotubes is that intensities arising from resonance with incident and scattered photons are equal. We present here the first complete Raman excitation profiles (REPs) for the

PDH-locked, frequency-stabilized cavity ring-down spectrometer

June 16, 2011
Author(s)
Joseph T. Hodges, A. Cygan, Piotr Maslowski, Katarzyna E. Bielska, S. Wojtewicz, J. Domyslawska, Hisashi Abe, R.S. Trawinski, R. Ciurylo
We describe a high sensitivity and high spectral resolution laser absorption spectrometer based upon the frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) technique. We used the Pound-Drever-Hall (PDH) method to lock the probe laser to the high

Controlled Vapor Deposition Approach to Generating Surface Energy/Chemistry Gradients

June 9, 2011
Author(s)
Julie N. Albert, Joey D. Kim, Christopher Stafford, Thomas H. Epps
Substrate surface energy/chemistry gradients provide a means for high-throughput exploration of the surface interactions that are important for many chemical and biological processes. We describe the implementation of a controlled vapor deposition approach

Bridging the Micro to Macro Gap: A New Application for Milli-probe X-ray Fluorescence

June 1, 2011
Author(s)
Jeffrey M. Davis, Dale E. Newbury, Nicholas W. Ritchie, Edward P. Vicenzi, Dale P. Bentz, Albert J. Fahey
X-ray elemental mapping and x-ray spectrum imaging are powerful microanalytical tools. However, their scope is limited spatially by the raster area of a scanning electron microscope or microprobe. Limited sampling size becomes a significant issue when

Electromagnetic Metrology on Concrete and Corrosion

June 1, 2011
Author(s)
Sung Kim, Jack T. Surek, James R. Baker-Jarvis
To go beyond current electromagnetic nondestructive evaluation (NDE) methods for reinforcing bar (rebar) corrosion we are exploring unique magnetic or electric spectral features and whether these might be prominent enough at the concrete cover depth to

Amplification of the optical absorption cross section for aerosols of soot with a nonabsorbing coating from photoacoustic measurements

May 13, 2011
Author(s)
Pedro Bueno, Daniel K. Havey, George W. Mulholland, Joseph T. Hodges, Keith A. Gillis, Russell R. Dickerson, Michael R. Zachariah
A quantitative understanding of the absorption and scattering properties of mixed soot and aerosol particles is necessary for evaluating the Earth's energy balance. Uncertainty in the net radiative forcing of atmospheric aerosols is relatively large and

Comparison of Diesel Fuel Oxygenates with Composition-Explicit Distillation Curve Method Part 1: Linear Compounds with One to Three Oxygens

May 2, 2011
Author(s)
Thomas J. Bruno, Tara Lovestead, Jennifer Riggs, Erica Jorgensen, Marcia L. Huber
There is a great deal of interest in formulating oxygenated diesel fuels that produce low particulate emissions. The most common oxygenating additives for diesel fuels include the glycol ethers, glycol esters, alcohols, ethers and ketones. It is important

Characterization of the First Order Nonlinear Stiffened Elasticity of the Piezoelectric Layer in Bulk Acoustic Wave Resonators

May 1, 2011
Author(s)
Juan C. Collado Gomez, Eduard Rocas, Jordi Mateu, Nathan D. Orloff, James C. Booth, Alberto Padillo, Juan Callaghan
This work proposes a procedure to characterize the intrinsic nonlinearities of bulk acoustic wave resonators by performing one port measurements of the second harmonic and second order intermodulation spurious signals. Closed-form expressions have been

Dual comb spectroscopy from 1.25 to 1.7 ym

May 1, 2011
Author(s)
Alexander M. Zolot, Ian R. Coddington, Fabrizio R. Giorgetta, Esther Baumann, William C. Swann, Nathan R. Newbury
A coherent dual comb spectrometer spanning much of the near infrared was constructed from broadened erbium fiber lasers. Gas phase water, methane and acetylene spectra were measured and characterized toward establishing new frequency standards.

Conformer-specific vibronic spectroscopy and vibronic coupling in a flexible bichromophore: bis-(4-hydroxyphenyl)methane

April 28, 2011
Author(s)
Chirantha P. Rodrigo, Christian Muller, Nathan Pillsbury, William H. James III, David F. Plusquellic, Timothy Zwier
The vibronic spectroscopy of jet-cooled bis-(4-hydroxyphenyl)methane (b4HPM) has been explored using fluorescence excitation (FE), dispersed fluorescence (DFL), UV-UV holeburning (UVHB), UV depletion (UVD), and fluorescence-dip infrared (FDIR)

High Pressure Viscosity Measurements of 1,1,1,2-Tetrafluoroethane

April 27, 2011
Author(s)
Arno R. Laesecke, Scott Bair
Viscosity measurements have been carried out with a falling-cylinder instrument in the compressed liquid and supercritical region of the hydrofluorocarbon 1,1,1,2-tetrafluoroethane (R134a). A highly pure sample was used. The measurement region at

Chirped-pulse terahertz spectroscopy for broadband trace gas sensing

April 22, 2011
Author(s)
Eyal Gerecht, Kevin O. Douglass, David F. Plusquellic
We report the first demonstration of a broadband trace gas sensor based on chirp-pulse terahertz spectroscopy. The advent of newly developed solid state sources and heterodyne detectors for the terahertz frequency range have made it possible to generate

Recent Advances in Electrochemical Glyco-biosensing

April 8, 2011
Author(s)
Rebecca A. Zangmeister, Germarie Sanchez-Pomales
Biosensors based on electrochemical transduction mechanisms have recently made advances into the field of glycan analysis. These glyco-biosensor assays offer simple, rapid, sensitive and economical approaches to the measurement need for rapid glycan
Displaying 1051 - 1075 of 2028