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)