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