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Physics

Spectroscopy

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Displaying 701 - 725 of 927

A Microwave Study of Hydrogen-Transfer-Triggered Methyl-Group Rotation in 5-Methyltropolone

November 10, 2010
Author(s)
Vadim V. Ilyushin, Emily A. Cloessner, Yung-Ching Chou, Laura B. Picraux, Jon T. Hougen, Richard Lavrich
We present here the first experimental and theoretical study of the microwave spectrum of 5-methyltropolone, which can be visualized as a 7-membered aromatic carbon ring with a five-membered hydrogen-bonded cyclic structure at the top and a methyl group at

High precision, broadband optical measurements with fiber laser frequency combs

November 2, 2010
Author(s)
Nathan R. Newbury, Ian R. Coddington, Esther Baumann, Fabrizio R. Giorgetta, William C. Swann, Alexander M. Zolot
Optical frequency combs have been used extensively, and with remarkable success, to measure the absolute frequency of cw lasers. The use of frequency combs has also expanded to include applications such as precision ranging, component metrology, and

Towards More Accurate Atomic Oscillator Strengths

October 28, 2010
Author(s)
Wolfgang L. Wiese, Jeffrey R. Fuhr, John M. Bridges
Accurate determinations of atomic oscillator strengths have been a problem for a long time, and discrepancies between various numerical results have been substantial. But in recent years considerable progress has been made, especially for weak lines

Fast high-resolution frequency agile spectroscopy of laser sources

October 24, 2010
Author(s)
Fabrizio R. Giorgetta, Ian R. Coddington, Esther Baumann, William C. Swann, Nathan R. Newbury
Time-resolved, high-accuracy and high-resolution spectroscopy of frequency-agile cw lasers is critical to realizing their full potential for sensing, but is not possible with conventional spectroscopy methods. We demonstrate a dual comb-based spectrometer

Organic Compounds in the C3H6O3 Family: Microwave Spectrum of cis-cis-Dimethyl Carbonate

October 18, 2010
Author(s)
Francis J. Lovas, David F. Plusquellic, Susanna L. Widicus Weaver, B. A. McGuire, G. A. Blake
Geometry optimization calculations on 13 members of the C3H6O3 family of organic species have been carried out to determine their relative binding energies. Dimethyl carbonate [(CH3)2CO3] is one of the lower energy species in this family, which includes

Thermochemistry of Ammonium Nitrate, NH4NO3, in the Gas Phase

October 7, 2010
Author(s)
Karl K. Irikura
Hildenbrand and coworkers have shown recently that the vapor above solid ammonium nitrate includes molecules of NH4NO3, not only NH3 and HNO3 as previously believed. Their measurements led to thermochemical values that imply an enthalpy change of D298 = 98

Revised interpretation of the Na I EUV absorption spectrum

September 27, 2010
Author(s)
Alexander Kramida
Spectral data for neutral sodium were recently compiled by Sansonetti (2008 J. Phys. Chem. Ref. Data 37 1659). In that compilation, some of the energy levels of the 2p53snl configurations were quoted from the studies of the absorption spectrum in the

X-Ray Spectroscopy of Highly Charged Ions in Laboratory and Astrophysical Plasmas

September 1, 2010
Author(s)
E. H. Silver, N Brickhouse, T. Lin, G X. Chen, K. Kirby, John D. Gillaspy, Joseph N. Tan, J M. Laming
This paper presents (1) new laboratory data on the x-ray spectra of He-like Ar XVII over a broad spectral range (300-3500 eV) at high resolution (2) the results of new measurements of K-shell x- ray reference lines in carbon, oxygen, iron, copper, and

Broadband coherent spectroscopy in the near infrared using dual coherent frequency combs

August 15, 2010
Author(s)
Nathan R. Newbury, Ian R. Coddington, Esther Baumann, Fabrizio R. Giorgetta, William C. Swann, Alexander M. Zolot
Fiber-based frequency combs can provide broadband coherent light that enables new possibilities for high-accuracy, high-resolution broadband spectroscopy. We use a configuration with two coherently phase-locked combs; the output of one comb passes through

Spectroscopy with a coherent dual frequency comb interferometer at 3.4 mm

August 1, 2010
Author(s)
Esther Baumann, Fabrizio R. Giorgetta, Ian R. Coddington, William C. Swann, Nathan R. Newbury
A coherent dual fiber-comb spectrometer centered at 1.5 µm wavelengths is transferred to 3.4 µm by difference-frequency generation with a 1064 nm cw laser. It is shown that the residual linewidth between the comb teeth at 3.4 µm is resolution-limited to

Ettore Majorana and the birth of autoionization

July 2, 2010
Author(s)
Charles W. Clark, Ennio Arimondo, William C. Martin
In the early days of theoretical atomic spectroscopy, Ettore Majorana (1906-1938?) solved several outstanding problems by developing the theory of autoionization. Later literature makes only sporadic references to this accomplishment. Reviewing his work in

Standard Photoacoustic Spectrometer: Model and Validation using O2 A-Band Spectra

June 30, 2010
Author(s)
Keith A. Gillis, Daniel K. Havey, Joseph T. Hodges
We model and measure the absolute response of an intensity-modulated photoacoustic spectrometer comprising a 10 cm long resonator and having a Q-factor of approximately 30. We present a detailed theoretical analysis of the system and predict its response

Measurement of residual stress field anisotropy at indentations in silicon

June 23, 2010
Author(s)
Yvonne B. Gerbig, Stephan J. Stranick, Robert F. Cook
The residual stress field around spherical indentations on single crystal silicon (Si) of different crystallographic orientation is mapped by confocal Raman microscopy. All orientations exhibit an anisotropic stress pattern with an orientation specific

High frequency characterization of a Schottky contact to a GaN nanowire bundle

June 16, 2010
Author(s)
Chin J. Chiang, Thomas M. Wallis, Dazhen Gu, Atif A. Imtiaz, Pavel Kabos, Paul T. Blanchard, Kristine A. Bertness, Norman A. Sanford, Kichul Kim, Dejan Filipovic
A GaN nanowire (NW) Schottky contact was characterized up to 10 GHz. Using a calibration procedure and circuit model a capacitance-voltage (CV) curve was obtained, from which a carrier concentration was calculated for the first time. These results

Tunable laser spectroscopy referenced with dual frequency combs

June 15, 2010
Author(s)
Fabrizio R. Giorgetta, Ian R. Coddington, Esther Baumann, William C. Swann, Nathan R. Newbury
Frequency combs provide broadband spectroscopic measurements with high frequency accuracy and precision. However, because the comb power is distributed over a broad spectrum, the sensitivity can be low unless some form of multiplexed detection or cavity
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