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Search Publications by: Joseph N. Tan (Fed)

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Displaying 26 - 50 of 132

Multiply-ionized Atoms Isolated at low energy in a Unitary Penning Trap

January 9, 2015
Author(s)
Joseph N. Tan, Shannon Hoogerheide, Samuel M. Brewer, Nicholas D. Guise
Ions extracted from the EBIT at NIST are slowed and captured in a Penning trap that is made very compact ( 150 cm3) by a unitary architecture. Measurements after 1 ms of ion storage indicate that the captured ions are distributed with 5(1) eV of energy

Tests of Theory in Rydberg States of One-electron Ions

July 1, 2014
Author(s)
Joseph N. Tan, Peter J. Mohr
Comparison of optical frequency measurements to predictions of quantum electrodynamics (QED) for Rydberg states of one-electron ions can test theory and allow new determinations of constants of nature to be made. Simplifications in the QED theory of high

Measurement of the Kr XVIII 3d 2D5/2 lifetime in a Unitary Penning Trap

April 24, 2014
Author(s)
Nicholas D. Guise, Joseph N. Tan, Samuel M. Brewer, Charlotte F. Fischer, P. Jonsson
The lifetime of the 3d 2D5/2 in the fine-structure doublet of the Kr XVIII ground configuration is measured using a compact Penning trap with 2.2 cm3 of trapping volume. Kr17+ ions produced in an electron beam ion trap (EBIT) are extracted and captured in

Capture and isolation of highly-charged ions in a compact Penning trap: V12

December 4, 2013
Author(s)
Samuel M. Brewer, Nicholas D. Guise, Joseph N. Tan
Room-temperature, compact Penning traps have been shown recently to be useful for capture and storage of highly-charged ions extracted from an EBIT ion source at the National Institute of Standards and Technology (NIST). Highly-charged argon and neon ions

Light polarization and quantum interference effects in unresolvable atomic lines: application to a precise measurement of the 6,7Li D2 lines.

March 7, 2013
Author(s)
Roger C. Brown, Saijun Wu, James V. Porto, Craig J. Sansonetti, Clayton Simien, Samuel M. Brewer, Joseph N. Tan, John D. Gillaspy
We characterize the effect of quantum interference of light scattering on the line shapes and measured line positions in atomic spectra. These effects occur when the excited state splittings are of order the excited state line widths, and represent an

Testing Three-body Quantum Electrodynamics with Trapped Ti-20 Ions: Evidence for a Z-Dependent Divergence between Experiment and Calculation

October 10, 2012
Author(s)
Lawrence T. Hudson, C T. Chantler, Mark N. Kinnane, John D. Gillaspy, A.T. Payne, L F. Smale, Albert Henins, Joseph N. Tan, J A. Kimpton, E Takacs, K Makonyi, Joshua M. Pomeroy
We report the measurement of the w (1s2p 1P1 ! 1s2 1S0) resonance line transition energy in helium-like titanium. Our result, 4749.85(7) eV, deviates from the most recent ab initio prediction by three times our experimental uncertainty and by many times

Towards One-electron Ions in Rydberg States for Laser Spectroscopy

July 30, 2012
Author(s)
Joseph N. Tan, Samuel M. Brewer, Nicholas D. Guise
Simple quantum systems play important roles in the determination of fundamental constants. Very recently at NIST, bare nuclei created in an EBIT were extracted and captured in a novel compact Penning trap. This is a step towards production of one-electron

Highly Charged Ions in Rare Earth Permanent Magnet Penning Traps

July 13, 2012
Author(s)
Nicholas D. Guise, Samuel M. Brewer, Joseph N. Tan
A newly constructed apparatus at the United States National Institute of Standards and Technology (NIST) is designed for the isolation, manipulation, and study of highly charged ions. Highly charged ions are produced in the NIST electron-beam ion trap

Penning traps with unitary architecture for storage of highly charged ions

February 15, 2012
Author(s)
Joseph N. Tan, Samuel M. Brewer, Nicholas D. Guise
Penning traps are made extremely compact by embedding rare-earth permanent magnets in the electrode structure. Axially-oriented NdFeB magnets are used to produce 0.32 T for ion trapping in unitary architectures that functionally couple the electric and

Absolute transition frequencies and quantum interference in a frequency comb based measurement of the 6,7Li D lines

July 6, 2011
Author(s)
Craig J. Sansonetti, Clayton Simien, John D. Gillaspy, Joseph N. Tan, Samuel M. Brewer, Roger C. Brown, Saijun Wu, James V. Porto
Optical frequencies of the D lines of 6,7Li were measured with a relative accuracy of 5x10-11 using an optical comb synthesizer. Quantum interference in the laser induced fluorescence for the partially-resolved D2 lines was found to produce polarization

Experiment at NIST towards one-electron ions in circular Rydberg states

June 20, 2011
Author(s)
Joseph N. Tan, Samuel M. Brewer, Nicholas D. Guise
An experimental effort is underway at NIST to enable tests of theory with oneelectron ions synthesized in circular Rydberg states from captured bare nuclei. Problematic effects which limit the accuracy of predicted energy levels for low-lying states are

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