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Displaying 1726 - 1750 of 2503

Interstellar Carbodiimide (HNCNH) - A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features

October 1, 2012
Author(s)
Brett A. McGuire, Ryan A. Loomis, Cameron M. Charness, Geoffery A. Blake, Jan M. Hollis, Francis J. Lovas, Philip R. Jewell, Anthony J. Remijan
Historically, searches for new astronomical molecules resulted in the detection of favorable, high line strength transitions based on a thermal approximation to the excitation of these species in interstellar environments. Given the temperatures of hot

Microsecond Accuracy at Multiple Locations: Is it possible without GPS?

October 1, 2012
Author(s)
Michael A. Lombardi
The microsecond is the most discussed unit in industrial timing systems, because microsecond accuracy is required to support critical infrastructure. Most critical infrastructure timing systems depend upon GPS, simply because microsecond accuracy is easy

Multiexciton dynamics in infrared-emitting colloidal nanostructures probed by a superconducting nanowire single-photon detector

September 30, 2012
Author(s)
Richard L. Sandberg, Lazaro A. Padilha, Mumtaz Qazilbash, Wan Ki Bae, Richard D. Schaller, Jeffrey M. Pietryga, Martin Stevens, Burm Baek, Sae Woo Nam, Victor I. Klimov
Carrier multiplication (CM) is the process in which absorption of a single photon produces multiple electron-hole pairs. Here, we evaluate the effect of particle shape on CM efficiency by conducting a comparative study of spherical nanocrystal quantum dots

The Habitable-Zone Planet Finder: A Stabilized Fiber-Fed NIR Spectrograph for the Hobby-Eberly Telescope

September 24, 2012
Author(s)
Scott A. Diddams, Suvrath Mahadevan, Lawrence W. Ramsey, Chad F. Bender, Ryan Terrien, Jason T. Wright, Samuel Halverson, Fred Hearty, Matthew Nelson, Adam Burton, Stephen L. Redman, Steve Osterman, James Kasting, Michael Endl
We present the scientific motivation and conceptual design for the recently funded Habitable-zone Planet Finder (HPF), a stabilized fiber-fed near-infrared (NIR) spectrograph for the 10 meter class Hobby-Eberly Telescope(HET) that will be capable of

Spin Dynamics in the Time and Frequency Domain

September 15, 2012
Author(s)
Thomas J. Silva
The current status of experimental approaches to analyze the spin wave dynamics in ferromagnetic nanoscale structures is reviewed. Recent developments in frequency- and field swept spectroscopy to determine the resonant response of nanoscale ferromagnets

Zero-energy modes and gate-tunable gap in graphene on hexagonal boron nitride

September 13, 2012
Author(s)
Markus Kindermann, Bruno Uchoa, David L. Miller
In this article, we derive an effective theory of graphene on a hexagonal boron nitride (h-BN) substrate. We show that the h-BN substrate generically opens a spectral gap in graphene despite the lattice mismatch. The origin of that gap is particularly

100-Fold Reduction of Electric-Field Noise in an Ion Trap Cleanded with In Situ Argon-Ion-Beam Bombardment

September 7, 2012
Author(s)
Dustin Hite, Yves Colombe, Andrew C. Wilson, Kenton R. Brown, Ulrich J. Warring, Robert Jordens, John D. Jost, David P. Pappas, Dietrich Leibfried, David J. Wineland, Kyle McKay
Anomalous heating of trapped atomic ions is a major obstacle to their use as quantum bits in scalable quantum computers. The physical origin of this electric field noise is not fully understood, but experimental evidence suggests that it emanates from the

Ultrafast manetization enhancement in metallic multilayers driven by superdiffusive spin current

September 4, 2012
Author(s)
Thomas J. Silva, Justin M. Shaw, Hans T. Nembach, Dennis Rudolf, Chan La-O-Vorakiat, Marco Battiato, Roman Adam, Emrah Turgut, Stefan Mathias, Margaret M. Murnane, Henry C. Kapteyn, Claus M. Schneider
Uncovering the physical mechanisms that govern ultrafast charge and spin dynamics is crucial for understanding correlated matter as well as the fundamental limits of ultrafast spin-based electronics. Spin dynamics in magnetic materials can be driven by

A Sub-Sampling Digital PM/AM Noise Measurement System

September 1, 2012
Author(s)
Craig W. Nelson, David A. Howe
A digital phase/amplitude modulation (PM/AM) noise measurement systems (DNMS) implementing field progammable gate array (FPGA) based digital down converters (DDCs), and 250 MHz analog to digital converters (ADCs) is reported. Measurements in the first

Simulating Quantum Magnetism with Correlated Non-Neutral Ion Plasmas

August 27, 2012
Author(s)
John J. Bollinger, Joseph W. Britton, Brian C. Sawyer
By employing forces which depend on the internal atomic state (or spin) of an atomic ion, the Coulomb potential energy of a strongly coupled array of ions can be modified in a spin-dependent way to mimic effective quantum spin Hamiltonians. Both

Coherent Diabatic Ion Transport and Separation in a Multizone Trap Array

August 24, 2012
Author(s)
Ryan S. Bowler, John P. Gaebler, Yiheng Lin, Ting Rei Tan, David Hanneke, John D. Jost, J. Home, Dietrich G. Leibfried, David J. Wineland
We investigate ion motion dynamics during the transport between and separation into spatially distinct trap locations in a multi-zone trap array. We laser-cool a single $\ensuremath{^{9}{\rm {Be}^{+}}}$ ion held in a linear Paul trap to near its ground

Optical isolator using an atomic vapor in the hyperfine Paschen-Back regime

August 15, 2012
Author(s)
Svenja A. Knappe, L. Weller, K.S. Kleinbach, M.A. Zentile, I.G. Hughes, C.S. Adams
A light, compact optical isolator using an atomic vapor in the hyperfine Paschen-Back regime is presented. Absolute transmission spectra for experiment and theory through an isotopically pure 87Rb vapor cell show excellent agreement for fields of 0.6 T. We

Scintillation Yield and Time Dependence from Electronic and Nuclear Recoils in Liquid Neon

August 13, 2012
Author(s)
Kevin J. Coakley, W. H. Lippincott, D. Gastler, E. Kearns, D. N. McKinsey, J. A. Nikkel
We have performed measurements of scintillation light in liquid neon, observing a signal yield in our detector as high as (3.5 +/- 0.04) photoelectrons/keV. We measure pulse shape discrimination between electronic and nuclear recoils in liquid neon between

Mid-infrared virtually imaged phased array spectrometer for rapid and broadband trace gas detection

August 1, 2012
Author(s)
Lora L. Nugent-Glandorf, Tyler W. Neely, Florian B. Adler, Adam J. Fleisher, Kevin C. Cossel, Bryce Bjork, Tim P. Dinneen, Chris S. Wood, Jun Ye, Scott A. Diddams
We present and analyze a 2-D imaging spectrometer based on a virtually imaged phased array (VIPA) disperser for rapid, high-resolution molecular detection using mid-infrared (MIR) frequency combs. A broad bandwidth, MIR laser source centered at ~3.1 υm

Calibration uncertainty for the NIST PM/AM noise standards

July 31, 2012
Author(s)
Archita Hati, Craig W. Nelson, Neil Ashby, David A. Howe
NIST provides an on-site calibration service of the accuracy of phase modulation (PM) noise, amplitude modulation (AM) noise and noise floor of the measurement systems at a customer's site using one or more portable PM/AM secondary noise standards. In this

Non-statistical population distributions for hydrogen beam in fusion plasmas

July 27, 2012
Author(s)
O. Marchuk, Yuri Ralchenko, D. R. Schultz
Most atomic models for a neutral hydrogen beam in fusion plasmas assume statistical (Boltzmann) distribution of populations for excited states with the same principal quantum number n. Here we analyze population distributions for the excited magnetic

Determination of graphene work function and graphene-insulator-semiconductor band alignment by internal photoemission spectroscopy

July 11, 2012
Author(s)
Rusen Yan, Qin Zhang, Wei Li, Irene G. Calizo, Tian T. Shen, Curt A. Richter, Angela R. Hight Walker, Xuelei X. Liang, David J. Gundlach, Nhan Van Nguyen, Huili G. Xing, Alan Seabaugh
We determined the band alignment of a graphene-oxide-silicon structure using internal photoemission spectroscopy. From the flatband voltage and Dirac voltage we infer a 4.3  10e11 cm-2 negative extrinsic charge present on the graphene surface. Also, we

Propagation of Vortex Electron Wave Functions in a Magnetic Field

July 5, 2012
Author(s)
Gregg M. Gallatin, Benjamin McMorran
The physics of coherent beams of photons carrying axial orbital angular momentum (OAM) is well understood and such beams, sometimes known as vortex beams, have found applications in optics and microscopy. Recently electron beams carrying very large values

100 Years of Superconductivity

July 2, 2012
Author(s)
Richard L. Kautz
The 100th anniversary of the discovery of superconudctivity by Heike Kamerlingh Onnes was celebrated in 2011 at the Superconductivity Centennial Conference held in The Hague. 100 Years of Superconductivity is a product of that celebration, but it's far

In-situ Polarized 3He system for the Magnetism Reflectometer at the Spallation Neutron Source

July 2, 2012
Author(s)
Thomas R. Gentile, X Tong, C Y. Jiang, V Lauter, H. Ambaye, D. Brown, L Crow, R J. Goyette, W-T Lee, A. Parizzi
We report on the in-situ polarized 3He neutron polarization analyzer developed for the time-of-flight Magnetism Reflectometer (MAGICS) at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). Using the spin exchange optical pumping
Displaying 1726 - 1750 of 2503
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