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Physics

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Displaying 2001 - 2025 of 2588

Fe xvii X-ray Line Ratios for Accurate Astrophysical Plasma Diagnostics

February 20, 2011
Author(s)
John D. Gillaspy, E. H. Silver, L. Tedesco, Joseph N. Tan, Joshua M. Pomeroy, J M. Laming, G.-X. Chen, T. Lin
New laboratory measurements of the Ne-like Fe xvii x-ray lines in the 15-17 Angstrom range are presented, along with new theoretical predictions. These results establish consistency between independent laboratories and opens the door to trustworthy

Enhanced magnetization drift velocity and current polarization in (CoFe)_{1-x}Ge_{x} alloys

February 17, 2011
Author(s)
Meng Zhu, Brian D. Soe, Robert D. McMichael, Matthew Carey, Stefan Maat, Jeffrey R. Childress
A spin wave Doppler technique is used to measure the drift velocity of the magnetization in current-carrying (CoFe)_{1-x}Ge_{x} alloys. For a current density of 10^11 A/m2, we obtain a large enhancement of drift velocity from 3.1+/-0.2 m/s for CoFe to 8.2+

Spherical Reference Cavities for Ultra-Stable Lasers in Non-Laboratory Environments

February 14, 2011
Author(s)
David R. Leibrandt, Michael J. Thorpe, Mark Notcutt, Robert E. Drullinger, Till P. Rosenband, James C. Bergquist
We present an ultra-stable optical cavity design that is insensitive to both vibrations and orientation. The design is based on a spherical cavity spacer which is held rigidly at two points on a diameter of the sphere. Coupling of the support forces to the

The Infrared Spectra of C2H4+ and C2H3 Trapped in Solid Neon

February 14, 2011
Author(s)
Marilyn E. Jacox, Warren E. Thompson
When a mixture of ethylene in a large excess of neon is codeposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, two groups of product absorptions appear in the infrared spectrum of the deposit. Similar studies using

Characterization of Power-to-Phase Conversion in High-Speed P-I-N Photodiodes

February 1, 2011
Author(s)
Jennifer A. Taylor, Shubahshish Datta, Archita Hati, Craig Nelson, Franklyn Quinlan, Abhay Joshi, Scott Diddams
Fluctuations of the optical power incident on a photodiode can be converted into phase fluctuations of the resulting electronic signal due to nonlinear saturation in the semiconductor. This impacts overall timing stability (phase noise) of microwave

The program LOPT for least-squares optimization of energy levels

February 1, 2011
Author(s)
Alexander Kramida
The article describes a program that solves the least-squares optimization problem for finding the energy levels of a quantum-mechanical system based on a set of measured energy separations or wavelengths of transitions between those energy levels, as well

Use of Phosphor Image Plates for Measuring Intensities in Vacuum Ultraviolet Spectra

January 28, 2011
Author(s)
Gillian Nave, Craig J. Sansonetti, Csilla Szabo, John J. Curry, Darren Smillie
We describe the use of phosphor image plates for recording spectra in the vacuum ultraviolet (VUV) and for determining accurate relative and absolute intensities. We investigated the spatial uniformity, noise level, linearity of the response to VUV light

Quantum information processing and metrology with trapped ions

January 25, 2011
Author(s)
David J. Wineland, Dietrich G. Leibfried
The use of trapped atomic ions in the field of quantum information processing is briefly reviewed. We summarize the basic mechanisms required for logic gates and the use of the gates in demonstrating simple algorithms. We discuss the potential of trapped

Making optical atomic clocks more stable with 10 -16 level laser stabilization

January 23, 2011
Author(s)
Andrew D. Ludlow, Yanyi Jiang, Nathan D. Lemke, Richard W. Fox, Jeffrey A. Sherman, Long-Sheng Ma, Christopher W. Oates
The superb precision of an atomic clock is derived from its stability. Atomic clocks based on optical (rather than microwave) frequencies are attractive because of their potential for high stability, which scales with operational frequency. Nevertheless

NMR Characterization of the Formation Kinetics and Structure of Di-O-Benzylidene Sorbitol Gels Self-Assembled in Organic Solvents

January 19, 2011
Author(s)
David L. VanderHart, Jack F. Douglas, Steven Hudson, Joseph M. Antonucci, Elizabeth A. Wilder
The molecule 1,3:2,4-Di-O-Benzylidene sorbitol (DBS) is a common gelator that forms thermally reversible gels in diverse organic solvents. Solid state 13C and proton NMR techniques, along with electron microscopy, are utilized in an exploratory study of

EUV Spectral Lines of Highly-Charged Hf, Ta and Au Ions Observed with an Electron Beam Ion Trap

January 12, 2011
Author(s)
Ilija Draganic, Yuri Ralchenko, Joseph Reader, John D. Gillaspy, Joseph N. Tan, Joshua M. Pomeroy, Samuel M. Brewer, Dmitry D. Osin
Extreme ultraviolet spectra of highly charged hafnium, tantalum, and gold were produced with an electron beam ion trap (EBIT) at the National Institute of Standards and Technology (NIST) and recorded with a flat-field grazing-incidence spectrometer in the

NIST Time and Frequency Bulletin

January 5, 2011
Author(s)
Petrina C. Potts
The Time and Frequency Bulletin provides information on performance of time scales and a variety of broadcasts (and related information) to users of the NIST services.

Femtotesla atomic magnetometry in a microfabricated vapor cell

December 20, 2010
Author(s)
William C. Griffith, Svenja A. Knappe, John Kitching
We describe an optically pumped 87Rb magnetometer with 4.5 fT/Hz 1/2 sensitivity when operated in the spin-exchange relaxation free (SERF) regime. The magnetometer uses a microfabricated vapor cell, consisting of a cavity etched in a 1 mm thick silicon

Progress at NIST in measuring the D-lines of Li isotopes using an optical frequency comb

December 20, 2010
Author(s)
Clayton Simien, Samuel M. Brewer, Joseph N. Tan, John D. Gillaspy, Craig J. Sansonetti
Precise spectroscopic experiments with light atoms can provide information about nuclear properties that are very difficult to obtain in electron scattering experiments. For example, relative nuclear radii of low-Z isotopes can be determined accurately

Polarized neutron beam properties for measuring parity-violating spin rotation in liquid He4

December 14, 2010
Author(s)
A M. Micherdzinska, C. D. Bass, T. D. Bass, K. F. Gan, D Lou, D M. Markoff, Hans Pieter Mumm, Jeffrey S. Nico, A. K. Opper, E I. Sharapov, M Snow, H E. Swanson, V Zhumabekova
Measurements of parity-violating neutron spin rotation can provide insight into the poorly nderstood nucleon-nucleon weak interaction. Because the expected rotation angle per unit length is small (10−7 rad/m), several properties of the polarized cold

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 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
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