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Physics

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Displaying 1151 - 1175 of 2574

AC Signal Characterization for Optimization of a CMOS Single Electron Pump

January 8, 2018
Author(s)
Roy E. Murray, Justin K. Perron, Michael D. Stewart, Neil M. Zimmerman
Pumping single electrons at a set rate is being widely pursued as an electrical current standard. Much work has been done on pumping using a single AC signal, but using multiple coordinated AC signals may help lower error rates. Whether pumping with one or

Quantum for Pressure

January 5, 2018
Author(s)
Jay H. Hendricks, Patrick F. Egan, Jacob E. Ricker, Jack A. Stone Jr., Kevin O. Douglass, Gregory F. Strouse
A team of NIST scientists is working to fundamentally change the way that the unit of pressure is realized and disseminated, an effort that will lead to the elimination of mercury barometer pressure standards.

Relativistic all-order many-body calculation of energies, wavelengths, and M1 and E2 transition rates for the 3d^n configurations in tungsten ions

January 3, 2018
Author(s)
M S. Safronova, U I. Safronova, S. G. Porsev, M G. Kozlov, Yuri Ralchenko
Energy levels, wavelengths, magnetic-dipole and electric-quadrupole transition rates between the low-lying states are evaluated for W51+ to W54+ ions with 3dn (n = 2 to 5) electronic con gurations using an approach combining con guration interaction with

Incorporating an Optical Clock into a Time Scale

January 1, 2018
Author(s)
Jian Yao, Thomas E. Parker, Neil Ashby, Judah Levine
This paper discusses how to build a time scale with an intermittently-operated optical clock. In particular, it gives suggestions on how long and how often to run an optical clock. It also explores the benefits of having an optical clock in a time scale

Natural Uranium Radioactivity Solution Standard: SRM 4321d

December 27, 2017
Author(s)
Ronald Colle, Lizbeth Laureano-Perez, Svetlana Nour, Jerome J. LaRosa, Brian E. Zimmerman, Leticia S. Pibida, Denis E. Bergeron
A new natural uranium solution standard has been produced and will be disseminated by the National Institute of Standards and Technology (NIST) as Standard Reference Material 4321d. The standard is certified for the massic activities of 234U, 235U, and

Multivariable Extrapolation of Grand Canonical Free Energy Landscapes

December 21, 2017
Author(s)
Nathan Mahynski, Jeffrey R. Errington, Vincent K. Shen
We derive an approach for extrapolating the free energy landscape of multicomponent systems in the grand canonical ensemble, obtained from flat- histogram Monte Carlo simulations, from one set of temperature and chemical potentials to another. This is

High-harmonic generation in periodically poled waveguides

December 19, 2017
Author(s)
Daniel D. Hickstein, David R. Carlson, Abijith S. Kowligy, Matt Kirchner, Scott Domingue, Nima Nader, Henry R. Timmers, Alexander J. Lind, Gabriel G. Ycas, Margaret Murnane, Henry Kapteyn, Scott B. Papp, Scott A. Diddams
Optical waveguides made from periodically poled materials provide high confinement of light and enable the generation of new wavelengths via quasi-phase-matching, making them a key platform for nonlinear optics and photonics. However, such devices are not

Hyperpolarizability and Operational Magic Wavelength in an Optical Lattice Clock

December 19, 2017
Author(s)
Roger C. Brown, Nate B. Phillips, Kyle P. Beloy, William F. McGrew, Marco Schioppo, Robert J. Fasano, Gianmaria Milani, Xiaogang Zhang, Nathan M. Hinkley, Holly F. Leopardi, T H. Yoon, Daniele Nicolodi, Tara M. Fortier, Andrew D. Ludlow
Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may degrade clock

Prospects for Magnetic Field Communications and Location Using Quantum Sensors

December 14, 2017
Author(s)
Vladislav P. Gerginov, Fabio C. Da Silva, David A. Howe
Signal attenuation limits the operating range in wireless communications and location. To solve the reduced range problem, one can use low-frequency signals in combination with magnetic sensing. We propose the use of an optically-pumped magnetometer as a

Relativistic theory of the falling retroreflector gravimeter

December 12, 2017
Author(s)
Neil Ashby
We develop a relativistic treatment of interference between light reflected from a falling cube retroreflector in the vertical arm of an interferometer, and light in a reference beam in the horizontal arm. Coordinates that are nearly Minkowskian, attached

Measurements of the Newtonian Constant of Gravitation, G

November 30, 2017
Author(s)
Christian Rothleitner, Stephan Schlamminger
The Newtonian Constant of Gravitation G seems to be the fundamental constant that is most difficult to measure accurately. In the past three decades more than a dozen precision measurements were performed. Unfortunately the scatter of the data points is

Ultra-high contrast coherent population trapping resonances in a cold-atom microwave clock

November 29, 2017
Author(s)
Xiaochi Liu, V. I. Yudin, A. V. Taichenachev, John Kitching, Elizabeth Donley
A cold-atom coherent population trapping clock can achieve a better long-term frequency stability than similar clocks based on vapor cells, since long interrogation periods are possible without introducing systematic frequency shifts from buffer gases

CRITICALLY EVALUATED SPECTRAL DATA FOR NEUTRAL CARBON (C I)

November 22, 2017
Author(s)
Haris Kunari, Alexander Kramida
In this critical compilation, all known to us experimental data on the spectrum of neutral carbon were methodically evaluated and supplemented by parametric calculations with Cowan's code. The sources of experimental data vary from laboratory to

String-like Collective Motion and Diffusion in the Interfacial Region of Ice

November 20, 2017
Author(s)
Jack F. Douglas, Hao Zhang, Xuhang Tong, Xinyi Wang
We investigate the collective molecular motions and diffusion of water molecules in the mobile interfacial region of the secondary prismatic plane of hexagonal ice by molecular dynamics simulation based on the TIP4P/2005 water potential and metrologies of
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