The 2p-3d Electron Transition Multiplet of Ar+13:
A Stellar Density Diagnostic
Laura HeeterKristina Naranjo-Rivera
2003-04
Introduction
Applications
• Density and temperature diagnostic for astrophysics
- Stellar corona, solar flairs- Naturally occurring thermal plasma- Chandra Observatory x-ray data
L-shell spectral peaks• Simple Structure• Density sensitivity
(Å)
Lepson et al. Survey 2p-3d Ar+13 Spectral Peaks
Trabert et al. Study
3d15/2
3d13/2
2p23/2
Metastable State 2p1
3/2
Ground State 2p1
1/2
Forbidden Transition
• Metastable level- 9.7 ms atomic lifetime
Theory
3d15/2
3d13/2
2p23/2
Metastable State 2p1
3/2
Ground State 2p1
1/2
Forbidden Transition
Wavelength (Å)
• Dr. Ming Feng-Gu– Peak intensities will invert with
increased beam current density
– Increased excitation to metastable state 2p1
3/2
Hypothesis
• Sensitivity to beam current density
• Increased electron excitation to metastable level
Objective
Stellar Object
EBIT
Ar+13 Emission Spectra Density?
Density Ar+13 Emission SpectraElecton Beam Ion Trap
EBIT
Liquid Helium Reservoir
Liquid Nitrogen Reservoir
Trapping Region
Collector
Electron Gun
Superconducting Helmholtz Magnet
http://www-phys.llnl.gov/Research/EBIT/
Methods
Prepare EBIT Excite Ar to Ar+13Determine
Constant Beam Energy
Collect & AnalyzeSpectral Images
Calculate Intensity Ratios
Compare Experimental and Theoretical Data
Results
• Inverse relationship: beam current and
intensity ratio
Results vs. Theory
Wavelength (Å)
Comparison to Theoretical Models
Density (cm –3)
Ar+13 experimental dataMonoenergetic beam Maxwellian plasma model
Discussion
• Increased population of metastable state occurred as beam current density increased
• Accuracy promises Ar+13 as a useful density diagnostic
Further Studies
• Broader density range• Use other more abundant elements
– Mg, Fe, Ni, and more– Currently Fe+21 is being tested
Acknowledgements
• The EBIT Team – Dr. Peter Beiersdorfer– Edward Magee– Dr. Hui Chen– Dr. Elmar Träbert– Ming Feng-Gu
• Ms. Fruen and the Research Class
The 2p-3d Electron Transition Multiplet of Ar+13: A Stellar Density Diagnostic
Laura HeeterKristina Naranjo-Rivera
2003-04
Elaboration of Methods: Analyze Ar+13 Spectra
• Igor Pro
• N+5 calibration
• Sum like data
Calculate Intensity Ratios
R = (I (3d5/2→2p3/2) + I (3d3/2→2p3/2)) / I(3d3/2→2p1/2)