NIST Spectroscopic Research on Heavy Elements 2005 - 2009
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Transcript of NIST Spectroscopic Research on Heavy Elements 2005 - 2009
NIST Spectroscopic Research on Heavy Elements 2005 - 2009
Wolfgang L WieseNational Institute of Standards and
Technology (NIST), USA
General Objective: Determine experimentally and theoretically the atomic structure of heavy element atoms
and ions of importance for magnetic fusion energy research
Main approaches:
• Measurements of heavy element spectra with vacuum sparks, lasers and the Electron Beam Ion Trap (EBIT). (This device reaches now charge state 68+.)
• Supporting analysis with pertinent plasma codes.• Comprehensive critical compilations of atomic energy levels,
wavelengths and transition probabilities os selected heavy elements• Atomic structure calculations with sophisticated Hartree-Fock and
Dirac-Fock programs• Calculations of ionisation and excitation cross sections with the
Binary Encounter Bethe (BEB) model and derivatives• Analysis of the neutral chlorine spectrum with a wall-stabilized arc
ParticipantsExperimental Research: J. Reader, G. Nave,
J. Gillaspy, M. Bridges,* W. Wiese*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*R. Ibacache
*indicates Contractors or Guest Researchers
General Objective: Determine experimentally and theoretically the atomic structure of heavy element atoms
and ions of importance for magnetic fusion energy research
Main approaches:
• Measurements of heavy element spectra with vacuum sparks, lasers and the Electron Beam Ion Trap (EBIT). (This device reaches now charge state 68+.)
• Supporting analysis with pertinent plasma codes.• Comprehensive critical compilations of atomic energy levels,
wavelengths and transition probabilities os selected heavy elements• Atomic structure calculations with sophisticated Hartree-Fock and
Dirac-Fock programs• Calculations of ionisation and excitation cross sections with the
Binary Encounter Bethe (BEB) model and derivatives• Analysis of the neutral chlorine spectrum with a wall-stabilized arc
The EBIT not only creates a highly charged ions, but can hold 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)
Ion production, trapping, and excitation
http://physics.nist.gov/ebit
EBIT on a table top
EBIT Internal View
107 K plasma
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)
• operates at 65 mK
• absorber: a foil of superconducting tin
• thermistor: neutron transmutation-doped (NTD) germanium
Quantum Microcalorimeter
“Crystal-quality” resolution, wide bandwidth and 100% efficiency.
L-shell
K-shell
Ar
Spectra and wavenumbers, as a function of element (Z)
Spectra as a function of electron beam energy
(Only a small subset shown. We have done this for several elements, extending as high as 24 keV for some)
Tungsten Data Tables from Recent Publications of the NIST EBIT Team
Includes new lines, and corrects misidentification from other groups.
Preliminary tables for >100 new lines presented at HCI and DAMOP conferences in 2006-2008
General Objective: Determine experimentally and theoretically the atomic structure of heavy element atoms
and ions of importance for magnetic fusion energy research
Main approaches:
• Measurements of heavy element spectra with vacuum sparks, lasers and the Electron Beam Ion Trap (EBIT). (This device reaches now charge state 68+.)
• Supporting analysis with pertinent plasma codes.• Comprehensive critical compilations of atomic energy levels,
wavelengths and transition probabilities os selected heavy elements• Atomic structure calculations with sophisticated Hartree-Fock and
Dirac-Fock programs• Calculations of ionisation and excitation cross sections with the
Binary Encounter Bethe (BEB) model and derivatives• Analysis of the neutral chlorine spectrum with a wall-stabilized arc
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
Recent Results:
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
Ionisation cross sections from the 3p54s levels
Ionisation cross sections from the 2p53s levels
Ar I
Excitation cross section from the metastable level 3p54s to 3p55p
General Objective: Determine experimentally and theoretically the atomic structure of heavy element atoms
and ions of importance for magnetic fusion energy research
Main approaches:
• Measurements of heavy element spectra with vacuum sparks, lasers and the Electron Beam Ion Trap (EBIT). (This device reaches now charge state 68+.)
• Supporting analysis with pertinent plasma codes.• Comprehensive critical compilations of atomic energy levels,
wavelengths and transition probabilities os selected heavy elements• Atomic structure calculations with sophisticated Hartree-Fock and
Dirac-Fock programs• Calculations of ionisation and excitation cross sections with the
Binary Encounter Bethe (BEB) model and derivatives• Analysis of the neutral chlorine spectrum with a wall-stabilized arc
Wall-Stabilized Arc
Wall-Stabilized Arc
Argon Mini Arc
Maxi Arc
Spectral Emission Analysis to determine Transition Probabilities (A)
• Arc Plasma operates at atmospheric pressure, electron density is about 1017 cm-3
• Local Thermodynamic Equillbrium (LTE) applies
• Line intensities I are measured to determine relative transition probabilities Ar initiating in atomic states m
I~(gm/λ) Ar exp(-Em/kT)
• Normalization to absolute A by one (or more) radiative lifetimes τ
τm =
and τm when there is one dominant transition
1
A
A
1
Bengtson et al (shock tube) vs NIST
±34%
Oliver a. Hibbert (CIV 3 Calc.) vs NIST
± 15%
Fischer (MCHF calc.) vs NIST
± 15%
Transition Wavelengthλ[Å]
NIST Expt.
Bengtsonet al
(1971)
Ojha & Hibbert(1990)
d (l-v) Singh et al.
(2006)
d (l-v) Oliver & Hibbert(2008)
d (l-v) Froese-Fischer(2006)
d (l-v)
4s 2P1/2-4p 2S1/2 9047.92 0.2644±15%
---------- 0.2865 11.9% 0.1852 51.3% 0.2519 3.0% 0.2639E-04 96.9%
4s 2P3/2-4p 2S1/2 8552.79 0.0085±25%
0.0188±52%
0.0177 17.3% 0.1621 11.4% 0.04424 18.3% 0.2776 8.2%
A-values for the 4s 2P -4p 2S doublet of Cl I
d (l-v) is the relative difference between the dipole-length and velocity results
An Example:
Experiments C a l c u l a t i o n s
Summary of principal NIST contributions to the IAEA CRP on Heavy Elements Investigations of spectra of heavy elements: Cl I, Ar I, Fe IV, Kr I, Xe VII to Xe XLIV, W XL to W XLVIII, W LV to W LXIV Calculations of cross sections: Ar I(ionization, BEB), Ar I(excitation, plane wave Born) Compilations of Reference Data: Energy Levels, Wavelengths: Kr I to Kr XXXVI, W I to WLXXIV(510 pages!) Ionization Energies: WIII to W LXXII Transition Probabilities: Al I to Al XIII, Si I to Si XIV, Fe I and Fe II