spectroscopic research projects on heavy elements at nist
DESCRIPTION
Spectroscopic Research Projects on Heavy Elements at NIST. Wolfgang L. Wiese National Institute of Standards and Technology (NIST), USA. Participants. Experimental Research: J. Reader, G. Nave, J. Gillaspy, J. Pomeroy Theoretical Approaches: Ch. Froese-Fischer,* Y. Ralchenko,* - PowerPoint PPT PresentationTRANSCRIPT
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Spectroscopic Research Projects on Heavy Elements at NIST
Wolfgang L. Wiese
National Institute of Standards and Technology (NIST), USA
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Participants
Experimental Research: J. Reader, G. Nave, J. Gillaspy, J. Pomeroy
Theoretical Approaches: Ch. Froese-Fischer,* Y. Ralchenko,*Y.-K. Kim, * P. Stone*
Data Assessment and J. Reader, E. Saloman, Compilations: J. Fuhr, D. Kelleher,*
L. Podobedova,* A. Kramida,* W. Wiese*
Database Development: Y. Ralchenko,* __________ A. Kramida**indicates Contractors or Guest Researchers
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Some On-going Spectroscopic Research Projects on Heavy Elements at NIST
1. Experimental observations of the spectra of highly charged tungsten ions, in the range from W+35 to W+50, with an Electron Beam Ion Trap (EBIT) and their analysis.
2. Calculations of ionization and excitation cross-sections of neutral and singly ionized Mo and W with the Binary-Encounter-Bethe (BEB) model.
3. An updated and expanded critical compilation of spectroscopic reference data, focusing on better transition probabilities, for Fe I and Fe II.
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EBIT not only creates a HCIs, but can holds their center of mass at rest.
EBIT size ~ 1 m
This overcomes the primary limitation of large HCI facilities for precision
spectroscopy.
To first order, the relative Doppler shift is
/ =v/c
The NIST Electron Beam Ion Trap (EBIT)
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A simplified EBIT:
Intense Electron Beam (4,000 A/cm2)
Strong magnetic field (3 tesla)
Highly Charged Ions (up to Bi72+at NIST).
Creates (by electron impact ionization) Traps (by electric and magnetic fields) Excites (electron impact)
Ion cloud width ~ 150 m
2 cmUltrahigh vacuum (~10-10 torr)
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• operates at 65 mK
• absorber: a foil of superconducting tin
• thermistor: neutron transmutation-doped
(NTD) germanium
Quantum Microcalorimeter
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5000
4000
3000
2000
1000
0
87654321
5300
5250
5200
5150
5100
5050
4.784.764.744.724.704.68
The “Pre-microcalorimeter Compromise”
SiLi
Crystal
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“Crystal-quality” resolution, wide bandwidth and 100% efficiency.
L-shell
K-shell
Ar
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Some On-going Spectroscopic Research Projects on Heavy Elements at NIST
1. Experimental observations of the spectra of highly charged tungsten ions, in the range from W+35 to W+50, with an Electron Beam Ion Trap (EBIT) and their analysis.
2. Calculations of ionization and excitation cross-sections of neutral and singly ionized Mo and W with the Binary-Encounter-Bethe (BEB) model.
3. An updated and expanded critical compilation of spectroscopic reference data, focusing on better transition probabilities, for Fe I and Fe II.
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Electron-Impact Cross Section Database(http://physics.nist.gov/ionxsec)
M. A. Ali, K. K. Irikura, Y.-K. Kim, P. M. Stone
Already in the database:
1. Total ionization cross sections of neutral atoms and molecules, singly charged molecular ions (about 100)
2. Differential ionization cross sections of H, He, H2
3. Excitation cross sections of light atoms
New results to be added by summer, 2006:
4. Total ionization cross sections (direct + excitation-autoionization) of Mo, Mo+, W, W+ (joint work with KAERI, see graphs)—BEB model plus BE/E scaling of Born cross sections [Mo/Mo+ in Kwon, Rhee & Kim, Int. J. Mass Spectrometry, 245, 26 (2005)]
5. Excitation cross sections of H2 (see graphs)—BE scaling of Born cross sections
6. Ionization cross sections of Si, Ge, Sn, Pb, Cl, Br, I, Cl2, Br2, I2
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Some On-going Spectroscopic Research Projects on Heavy Elements at NIST
1. Experimental observations of the spectra of highly charged tungsten ions, in the range from W+35 to W+50, with an Electron Beam Ion Trap (EBIT) and their analysis.
2. Calculations of ionization and excitation cross-sections of neutral and singly ionized Mo and W with the Binary-Encounter-Bethe (BEB) model.
3. An updated and expanded critical compilation of spectroscopic reference data, focusing on better transition probabilities, for Fe I and Fe II.
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Fe I
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Fe I
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Fe II
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Fe II
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1988
2006
Fe I
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19882006
Fe II