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Physics

Spectroscopy

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Displaying 576 - 600 of 932

Time-Resolved Infrared Studies of a Trimethylphosphine Model Derivative of [FeFe]-Hydrogenase

October 1, 2013
Author(s)
Edwin J. Heilweil, Christopher J. Stromberg, Melissa Johnson, James Thuman, Roger G. Letterman, Webster E. Charles
Model compounds that structurally mimic the hydrogen-producing active site of [FeFe] hydrogenases have been explored. In order to explore potential ground-state electronic structure effects on reaction mechanisms compared to hexacarbonyl derivatives, the

Rapid scan absorption spectroscopy using a waveform-driven electro-optic phase modulator in the 1.6- 1.65 ym region

September 25, 2013
Author(s)
Kevin O. Douglass, Stephen Maxwell, Gar W. Truong, Roger D. van Zee, Joseph T. Hodges, David Long, David F. Plusquellic
A method is reported for performing fast optical frequency scans over a bandwidth of 36.9 GHz and at a sweep rate of 40 kHz using a single second-order sideband from an electro-optic phase modulator driven by an arbitrary waveform generator. Single

A Missing Link in the Cascade Formation of High Symmetry Fullerene Cages

September 15, 2013
Author(s)
Dan Bearden, Jianyuan Zhang, Harry C. Dorn
Before the discovery of graphene, many versions of a “bottom-up” fullerene formation mechanism had been advanced starting with carbide (C2) that forms small carbon cluster chains and rings. However, in recent years evidence is emerging suggesting a “top

Direct measurements of mass-specific optical cross sections of single component aerosol mixtures

July 22, 2013
Author(s)
James Radney, Xiaofei Ma, Keith A. Gillis, Michael R. Zachariah, Joseph T. Hodges, Christopher D. Zangmeister
The optical properties of atmospheric aerosols vary widely, being dependent upon particle composition, morphology and mixing state. This diversity and complexity of aerosols motivates measurement techniques that can discriminate and quantify a variety of

Anisotropic LMN dielectronic resonances from ratios of magnetic-dipole lines

July 13, 2013
Author(s)
Yuri Ralchenko, John D. Gillaspy
Signatures of multi-keV LMN dielectronic resonances in highly-charged 3dn ions of tungsten were detected in the intensity ratios of extreme-ultraviolet magnetic-dipole lines within ground configurations. The measurements were performed with an electron

Open-Path Dual-Comb Spectroscopy of Greenhouse Gases

June 9, 2013
Author(s)
Greg B. Rieker, Fabrizio R. Giorgetta, William C. Swann, Ian R. Coddington, Laura C. Sinclair, Christopher L. Cromer, Esther Baumann, Alexander M. Zolot, Nathan R. Newbury
Frequency-comb spectroscopy in the near-infrared is used to measure atmospheric CO2 and H2O concentrations over a 2-km outdoor open-air path. This technique shows promise for measurements over length scales between point sensors and satellite systems.

Transition Energies of the D-lines in Na-like Ions

June 5, 2013
Author(s)
John D. Gillaspy, Dmitry D. Osin, Yuri Ralchenko, Joseph Reader, S A. Blundell
The NIST electron beam ion trap (EBIT) was used to measure the D1 (3s-3p1/2) and D2 (3s-3p3/2) transitions in Na-like ions of xenon, barium, samarium, gadolinium, dysprosium, erbium, tungsten, platinum, and bismuth. New relativistic many-body perturbation

A fitting program for molecules with two equivalent methyl tops and C2v point-group symmetry at equilibrium: Application to existing microwave, millimeter, and sub-millimeter wave measurements of acetone

May 31, 2013
Author(s)
Jon T. Hougen, Vadim V. Ilyushin
A program, called PAM_C2v_2tops, for fitting the high-resolution torsion-rotation spectra of molecules with two equivalent methyl rotors and C2v symmetry at equilibrium is described and applied to the spectrum of acetone [(CH3)2CO]. The G36 permutation

Photochemical Properties of Some Cl-Containing Halogenated Alkanes

May 31, 2013
Author(s)
Vladimir L. Orkin, Victor Khamaganov, E. E. Kasimovskaya, A G. Guschin
Rate constants for the gas phase reactions of OH radicals with three partially halogenated alkanes, CHCl3 (kMC), CHFClCFCl2 (k122a), and CH2CFCl2 (k132c), were measured using a discharge flow – electron paramagnetic resonance technique over the temperature

Precision metrology with coherent dual frequency combs

May 12, 2013
Author(s)
Nathan R. Newbury, Esther Baumann, Ian R. Coddington, Fabrizio R. Giorgetta, Greg B. Rieker, Laura C. Sinclair, William C. Swann, Alexander M. Zolot
Frequency combs have enabled a wide range of applications because of their unique combination of coherence and broad bandwidth. The comb provides 100,000's of comb teeth at precise, well-known optical frequencies that can support broadband accurate

Differential cavity ring-down spectroscopy

May 9, 2013
Author(s)
Jeremie B. Courtois, Katarzyna E. Bielska, Joseph T. Hodges
We present a technique called differential cavity ring-down spectroscopy (D-CRDS) for reducing etaloning effects in a ring-down spectrometer. The method relies on alternately measuring and then subtracting intra-cavity losses associated with pairwise TEM00

Light-Wave Mixing with Quantum Gases

May 1, 2013
Author(s)
Lu Deng, Edward W. Hagley, R Q. Wang, Charles W. Clark
Nonlinear optics has come a long way since the laser. This article reviews recent progress in coherent light-matter wave mixing and introduces some new concepts that will reframe future research directions.

Frequency-agile, rapid scanning spectroscopy

April 28, 2013
Author(s)
Gar W. Truong, Kevin O. Douglass, Stephen E. Maxwell, Roger D. van Zee, David F. Plusquellic, Joseph T. Hodges, David A. Long
Challenging applications in trace gas analyses require high precision and acquisition rates.1-4 Many continuous-wave laser spectroscopy techniques exhibit significant sensitivity and potential;5 however, their scanning rates are slow because they rely upon

Evaluation of Pacific White Shrimp (Litopenaeus vannamei) Health During a Superintensive Aquaculture Growout using NMR-based Metabolomics

March 27, 2013
Author(s)
Tracey B. Schock, Dan Bearden, Jessica Duke, Abby Goodson, Daryl Weldon, Jeff Brunson, John Leffler
Success of the shrimp aquaculture industry requires technological advances that increase production and environmental sustainability. Indoor, superintensive, aquaculture systems have been developed that permit year-round production of farmed shrimp at high

Detection of E-cyanomethanimine (HCN-dimer) towards Sagittarius B2(N) from the GBT PRIMOS Survey

March 20, 2013
Author(s)
Francis J. Lovas, Daniel P. Zaleski, Nathan A. Seifert, Amanda L. Steber, Matt T. Muckle, Ryan A. Loomis, Joanna F. Corby, Oscar Martinez, Kyle Crabtree, Phillip R. Jewell, Jan M. Hollis, David Vasquez, Jolie Nyiramahirwe, Nicole Sciortino, Kennedy Johnson, Michael C. McCarthy, Anthony J. Remijan, Brooks H. Pate
An understanding of the formation, distribution and overall excitation of large molecules in astronomical environments remains in question even though more than 170 distinct chemical compounds have been detected in astronomical environments. Furthermore, a

Light polarization and quantum interference effects in unresolvable atomic lines: application to a precise measurement of the 6,7Li D2 lines.

March 7, 2013
Author(s)
Roger C. Brown, Saijun Wu, James V. Porto, Craig J. Sansonetti, Clayton Simien, Samuel M. Brewer, Joseph N. Tan, John D. Gillaspy
We characterize the effect of quantum interference of light scattering on the line shapes and measured line positions in atomic spectra. These effects occur when the excited state splittings are of order the excited state line widths, and represent an
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