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,*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

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.

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)

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

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

“Crystal-quality” resolution, wide bandwidth and 100% efficiency.

L-shell

K-shell

Ar

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.

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

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.

Fe I

Fe I

Fe II

Fe II

1988

2006

Fe I

19882006

Fe II