Laboratory Calibrations of Fe XII-XIV Line-Intensity Ratios for Electron Density Diagnostics

Abstract

We have used an electron beam ion trap to measure electron-density-diagnostic line-intensity ratios for extreme ultraviolet lines from F XII, XIII, and XIV at wavelengths of 185-205 255-276 Angstroms. These ratios can be used as density diagnostics for astrophysical spectra and are especially relevant to solar physics. We found that density diagnostics using the Fe XIII 196.53/202.04 and the Fe XIV 264.79/274.21 and 270.52A/274.21 line ratios are reliable using the atomic data calculated with the Flexible Atomic Code. On the other hand, we found a large discrepancy between the FAC theory and experiment for the commonly used Fe XII (186.85 + 186.88)/195.12 line ratio. These FAC theory calculations give similar results to the data tabulated in CHIANTI, which are commonly used to analyze solar observations. Our results suggest that the discrepancies seen between solar coronal density measurements using the Fe XII (186.85 + 186.88)/195.12 and Fe XIII 196.54/202.04 line ratios are likely due to issues with the atomic calculations for Fe XII.

References in corpus (3)

• CHIANTI - An atomic database for Emission Lines. Version 8
• EUV emission lines and diagnostics observed with Hinode/EIS
• High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII

Cited by in corpus (4)

• X-ray spectra of the Fe-L complex II: atomic data constraints from EBIT experiment and X-ray grating observations of Capella
• Quiet Sun electron densities and their uncertainties derived from spectral emission line intensities
• Fe XII and Fe XIII Line Widths in the Polar Off-limb Solar Corona up to 1.5 Rsun
• High-Resolution Laboratory Measurements of M-shell Fe EUV Line Emission using EBIT-I