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Search Publications by: Joseph N. Tan (Fed)

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Displaying 51 - 75 of 132

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

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

X-Ray Spectroscopy of Highly Charged Ions in Laboratory and Astrophysical Plasmas

September 1, 2010
Author(s)
E. H. Silver, N Brickhouse, T. Lin, G X. Chen, K. Kirby, John D. Gillaspy, Joseph N. Tan, J M. Laming
This paper presents (1) new laboratory data on the x-ray spectra of He-like Ar XVII over a broad spectral range (300-3500 eV) at high resolution (2) the results of new measurements of K-shell x- ray reference lines in carbon, oxygen, iron, copper, and

Fundamental constants and tests of theory in Rydberg states of one-electron ions

March 19, 2010
Author(s)
Ulrich D. Jentschura, Peter Mohr, Joseph N. Tan
The nature of the theory of circular Rydberg states of hydrogenlike ions allows highly-accurate predictions to be made for energy levels. In particular, uncertainties arising from the problematic nuclear size correction which beset low angular-momentum

Measurement of the D Line Doublet in High-Z Highly-Charged Sodium-like Ions

July 8, 2009
Author(s)
John D. Gillaspy, Ilija Draganic, Yuri Ralchenko, Joseph Reader, Joseph N. Tan, Joshua M. Pomeroy, Samuel M. Brewer
We report a direct observation of the D line doublet of sodium-like ions with Z≥72. Spectra in the 1 nm to 9 nm spectral range are presented showing the widely split doublet for Hf61+, Ta62+, W63+,and Au68+. The ions were produced and confined in an

Fundamental constants and tests of theory in Rydberg states of hydrogenlike ions

July 1, 2009
Author(s)
Ulrich D. Jentschura, Peter Mohr, Joseph N. Tan, Benedikt J. Wundt
A comparison of precision frequency measurements to quantum electrodynamic (QED) theoretical predictions can be used to test theory and to obtain information regarding fundamental constants. We find that for Rydberg states, theoretical uncertainties due to

Fundamental Constants and Tests of Theory in Rydberg States of Hydrogen-like Ions

April 22, 2008
Author(s)
Ulrich D. Jentschura, Peter Mohr, Joseph N. Tan, B. J. Wundt
A comparison of precision frequency measurements to quantum electrodynamics (QED) predictions for Rydberg states of hydrogen-like ions can yield information on values of fundamental constants and test theory. With the results of a calculation of a key QED

Spectra of W 39+ -W 47+ in the 12 nm to 20 nm Region Observed With an EBIT Light Source

October 14, 2007
Author(s)
Yuri Ralchenko, Joseph Reader, Joshua M. Pomeroy, Joseph N. Tan, John D. Gillaspy
We observed spectra of highly ionized tungsten in the extreme ultraviolet with an electron beam ion trap (EBIT) and a grazing incidence spectrometer at the National Institute of Standards and Technology. Stages of ionization were distinguished by varying

EUV Spectroscopy of Highly Charged Xenon Ions Created Using an Electron Beam Ion Trap

March 27, 2007
Author(s)
K Fahy, E Sokell, G O'Sullivan, A Aguilar, Joshua M. Pomeroy, Joseph N. Tan, John D. Gillaspy
At the NIST Electron Beam Ion Trap (EBIT), extreme-ultraviolet spectra of xenon ions have been recorded using a flat-field spectrometer. The electron beam energy was varied from 180 eV to 8 keV and radiation from charge states Xe6+ to Xe43+ was observed