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Physics

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  • Published Date
Displaying 1926 - 1950 of 2493

An optical frequency comb for infrared spectrograph calibration

November 17, 2010
Author(s)
Gabriel G. Ycas, Franklyn J. Quinlan, Steve Osterman, Gillian Nave, Craig J. Sansonetti, Scott A. Diddams
Detection of extrasolar planets by measurement of the stellar radial velocity shift requires high resolution spectroscopy with long term stability. Presently, the primary wavelength standards in the NIR are NePt and ThAr lamps and absorption cells. These

A Portable Rubidium Fountain

November 15, 2010
Author(s)
Paul D. Kunz, Steven R. Jefferts, Thomas P. Heavner
We are developing a transportable laser-cooled rubidium (Rb) atomic fountain frequency standard. Over the last year we have built the Ramsey cavity and rubidium source oven and are preparing to assemble the physics package. We have also made numerous

NIST F1 and F2

November 15, 2010
Author(s)
Thomas P. Heavner, Thomas E. Parker, Jon H. Shirley, Paul D. Kunz, Steven R. Jefferts
The National Institute of Standards and Technology operates a cesium fountain primary frequency standard, NIST-F1, which has been contributing to International Atomic Time (TAI) since 1999. During the intervening 11 years we have improved NIST-F1 so that

On-Board GPS Clock Monitoring for Signal Integrity

November 15, 2010
Author(s)
Marc A. Weiss, Pradipta Shome, Ron Beard
Navigation signal integrity is paramount for aviation and safety of life services. Hitherto GPS signal anomaly alerting has been provided primarily by ground based augmentations. Significantly improved navigation signal integrity and quality may be

Decoherence due to elastic Rayleigh scattering

November 12, 2010
Author(s)
Hermann Uys, Michael J. Biercuk, Aaron Vandevender, Christian Ospelkaus, Dominic Meiser, R. Ozeri, John Bollinger
We present theoretical and experimental studies of the decoherence of hyperfine ground-state superpositions due to elastic Rayleigh scattering of off-resonant light. We demonstrate that under appropriate conditions, elastic Rayleigh scattering can be the

Collective atomic recoil motion in short-pulse matter-wave superradiance

November 11, 2010
Author(s)
Lu Deng, Edward W. Hagley
We show that a Bragg resonance is substantially incapacitated in short-pulse, matter-wave superradiant scatterings and both positive- and negative-order scatterings contribute equally.We further show that propagation gain is small and scattering events

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

Electron ionization and gas-phase ion molecule reactions of methylcyclohexane

November 9, 2010
Author(s)
C. Q. Jiao, Karl Irikura, S, F. Adams, A Garscadden
Absolute cross sections for electron impact ionization of methylcyclohexane (MCH, C 7H 14) are measured as a function of the electron energy in a range of 10 to 200 eV. The reactions between selected hydrocarbon ions with MCH, mainly via hydride transfer

Consistency of atomic data for the interpretation of beam emission spectra

November 8, 2010
Author(s)
E. Delabie, M. Brix, R. J. Jasper, C. Giroud, O. Marchuk, M. G. O'Mullane, Yuri Ralchenko, E Surrey, M. G. von Hellermann, K. Zastrow, JET-EFDA Contributors
Several collisional-radiative (CR) models \citeanderson,hutchinson,marchuk:htpd} have been developed to calculate the attenuation and the population of excited states of hydrogen or deuterium beams injected into tokamak plasmas. The datasets generated by

Effect of metal/substrate interfaces on radio-frequency loss in superconducting coplanar waveguides

November 8, 2010
Author(s)
David S. Wisbey, Jiansong Gao, Fabio C. da Silva, Jeffrey S. Kline, Michael Vissers, David P. Pappas, Leila R. Vale
Microscopic two-level systems (TLSs) are known to contribute to loss in resonant superconducting microwave circuits. This loss increases at low power and temperatures as the TLSs become unsaturated. We find that the loss is dependent on both the substrate

Nuclear Magnetic Resonance Gyroscopes

November 2, 2010
Author(s)
Elizabeth A. Donley
Nuclear magnetic resonance gyroscopes(NMRGs)detect rotation as shift in the Larmor precession frequency of nuclear spins. A review of the open literature on NMRGs is presented, which includes an introduction to the spectroscopic techniques that enable

A comprehensive analysis of the spectrum of Fe II

October 28, 2010
Author(s)
Gillian Nave
A new analysis of the laboratory spectrum of Fe II is described. The aim is to produce a comprehensive list of Fe II lines, based on high-resolution grating and Fourier transform spectra, covering wavelengths from 900 ̊A to 5.5 μm. Particular attention has

Atomic Spectroscopic Databases at NIST

October 28, 2010
Author(s)
Joseph Reader, Alexander Kramida, Yuri Ralchenko
We present recent work at NIST to develop and maintain databases for spectra, transition probabilities, and energy levels of atoms that are astrophysically important. We also describe our programs to critically compile these data as well as the recently

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

SIM time scales

October 27, 2010
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz
This paper presents an analysis of the performance of some of the time scales generated in the Sistema Interamericano de Metrologia (SIM) region. We emphasize the generation of the first international time scale in near real time, the SIM Time scale (SIMT)

The evolving optical frequency comb

October 22, 2010
Author(s)
Scott A. Diddams
Much as natural historians search for the first roots of our human race, curiosity drives the laser scientist to pursue the roots of his or her own field. This is especially the case in this year where our community celebrates the 50th anniversary of the

Characterization of a Soluble Anthradithiophene Derivative

October 1, 2010
Author(s)
Brad Conrad, Calvin Chan, Marsha A. Loth, Sean R. Parkin, Xinran Zhang, John E. Anthony, David J. Gundlach
The structural and electrical properties of a new solution processable material, 2,8-diflouro-5,11-tert-butyldimethylsilylethynl anthradithiophene (TBDMS), were measured for single crystal and spun cast thin-film transistors. TBDMS is observed to readily
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