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NIST Authors in Bold

Displaying 1201 - 1225 of 2503

Telling Time

February 19, 2017
Author(s)
Jonathan E. Hardis
In Low-Tech Blues [June], you note that we are surrounded by clocks, but lament the lack of systems to set them automatically. Our job is to help fix that. Your readers can use our time servers (www. Bldrdoc.gov/timefreq/service/its.htm) to automatically

Ultra-Cold Collisions of Atoms and Molecules

February 19, 2017
Author(s)
Paul S. Julienne
The study of collisions of neutral atoms and molecules at ultralow collision energies is made possible by advances in techniques for cooling and trapping such species. Excellent reviews of laser cooling of atoms are given in the Nobel Lectures of Chu 2

Revised analysis of the fifth spectrum of rhenium (Re V)

February 17, 2017
Author(s)
Vladimir I. Azarov, R R. Gayasov
The spectrum of rhenium was observed in the (500 to 2100) A wavelength region. A 6.65 m normal incidence VUV spectrograph has been used to record the spectrum. The (5d3 + 5d26s) - 5d26p transition array of four times ionized rhenium, Re V, has been

NIST Time and Frequency Bulletin

February 9, 2017
Author(s)
Kathryn R. Stephenson
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.

Sympathetic Ground State Cooling and Time-dilation Shifts in an 27Al+ Optical Clock

February 3, 2017
Author(s)
Jwo-Sy Chen, Samuel M. Brewer, David B. Hume, Chin-Wen Chou, David J. Wineland, David R. Leibrandt
We report Raman sideband cooling of 25Mg+ to sympathetically cool the secular modes of motion in a 25Mg+-27Al+ two-ion pair to near the three-dimensional (3D) ground state. The evolution of the Fock state distributions during the cooling process is studied

Ultrafast modulation of x-ray absorption by coherent phonon excitations

February 1, 2017
Author(s)
Eric L. Shirley, Jannick Weisshaupt, Michael Woerner, Marc J. Vrakking, Thomas Elsaesser, Andreas Borgschulte
X-ray absorption in solids promotes an electron from an atomic core level to the conduction band states, and near-edge spectra structure gives insight into local atomic geometry and chemical bonding effects. Based on a novel implementation of femtosecond x

A Clock Ensemble Using Only Active Hydrogen Masers

January 31, 2017
Author(s)
Thomas E. Parker, Stefania Romisch
The current real-time timescale at NIST, AT1, as well as the post-processed scale TP162, both contain hydrogen masers and commercial cesium frequency standards. The cesium standards are much nosier in the short term than the hydrogen masers and

A Study on Using the SDR Receiver for the Europe-Europe and Transatlantic TWSTFT Links

January 31, 2017
Author(s)
Victor S. Zhang, Thomas E. Parker, Joseph Achkar, Dirk Piester, Yi-Jiun Huang, Shinn-Yan Lin, Zhiheng Jiang
The BIPM and the CCTF Working Group on TWSTFT have stimulated a pilot study on using software defined radio (SDR) receivers for TWSTFT in the framework of the realization of International Atomic Time (TAI). The SDR receivers based on a software developed

Accurate TWSTFT time transfer with indirect links

January 31, 2017
Author(s)
Victor S. Zhang, Zhiheng Jiang, Thomas E. Parker, Jian Yao, Yi-Jiun Huang, Shinn-Yan Lin
The conventional wisdom suggests a direct Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) time link should result in a smaller uncertainty than that of an indirect TW link over the same baseline [12]. This is why all Coordinated Universal Time

Local Distribution and Calibration of Timing Signals at NIST

January 31, 2017
Author(s)
Joshua J. Savory, Liz C. Forero, Kristopher Maurer, Stefania Romisch
The National Institute of Standards and Technology (NIST) timescale produces a real-time realization of UTC(NIST) in the form of a pulse-per-second (PPS) time signal and a 5 MHz frequency reference. The timing signals are distributed to the international

Long-term instability in UTC time links

January 31, 2017
Author(s)
Victor S. Zhang, Demetrios Matsakis, Zhiheng Jiang
Calibration and link stability are the key issues for the UTC time transfer. This study is made in the framework of a joint task group of the CCTF Working Group on TWSTFT and Working Group on GNSS Time Transfer to investigate the long-term instability of

The development of a new Kalman-filter time scale at NIST

January 31, 2017
Author(s)
Jian Yao, Thomas E. Parker, Judah Levine
We report on a preliminary design of a new Kalman-filter Hydrogen-maser time scale at NIST. The time scale is composed of a few Hydrogen masers and a Cs clock. The Cs clock is used as a reference clock, just for easy operations with the existing data. All

The effects of the January 2016 UTC offset anomaly on GPS clocks monitored at NIST

January 31, 2017
Author(s)
Jian Yao, Michael A. Lombardi, Andrew N. Novick, Bijunath Patla, Jeffrey A. Sherman, Victor S. Zhang
Errors in the Coordinated Universal Time (UTC) offset parameters broadcast by Global Positioning System (GPS) satellites caused many thousands of GPS clocks to be in error by approximately -13 µs on January 25-26, 2016. The erroneous UTC offset information

Trapped-ion optical atomic clocks at the quantum limits

January 31, 2017
Author(s)
David R. Leibrandt, Samuel M. Brewer, Jwo-Sy Chen, Aaron M. Hankin, David B. Hume, David J. Wineland, Chin-Wen Chou
Frequency and its inverse, time, are the most accurately measured quantities. Historically, improvements in the accuracy of clocks have enabled advances in navigation, communication, and science. Since 1967, the definition of the SI second has been based

A New Generation of Magnetoencephalography: Room Temperature Measurements using Optically-Pumped Magnetometers

January 25, 2017
Author(s)
Elena Boto, Sofie S. Meyer, Vishal Shah, Orang Alem, Svenja A. Knappe, Peter Kruger, Mark Fromhold, Peter G. Morris, Richard W. Bowtell, Gareth R. Barnes, Matthew J. Brookes, Mark Lim
Significant advances in the field of quantum sensing mean that magnetic field detectors, operating at room temperature, are now able to achieve sensitivity similar to that of cryogenically cooled devices (SQUIDs). This means that room temperature

A microfabricated optically-pumped magnetic gradiometer

January 18, 2017
Author(s)
Abigail R. Perry, Sean P. Krzyzewski, John E. Kitching, S. Geller, Sheng D., Svenja A. Knappe
We report on the development of a microfabricated atomic magnetic gradiometer based on optical spectroscopy of alkali atoms in the vapor phase. The gradiometer, with a length of 60 mm and a cross section diameter of 12 mm, is made of two chip-scale atomic

Coherent UV-to-Visible Light Arrays

January 9, 2017
Author(s)
Dong Yoon Oh, Scott Diddams, Ki Youl Yang, Kerry J. Vahala, Connor Fredrick, Gabriel Ycas
Short duration, intense pulses of light can experience dramatic spectral broadening when propagating through lengths of optical fiber. This continuum generation process is caused by a combination of nonlinear optical effects including the formation of so

Preflight Radiometric Calibration of Orbiting Carbon Observatory 2

January 9, 2017
Author(s)
Stephen Maxwell, B. Carol Johnson, Robert Rosenberg, Lars Chapsky, Richard A. Lee, Randy Pollock
This paper describes the prelaunch radiometric calibration of the imaging spectrometers used on the second Orbiting Carbon Observatory (OCO-2). The gain and dark response were characterized for each focal plane array detector element. An integrating sphere
Displaying 1201 - 1225 of 2503
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