• DOI:10.3847/1538-4357/abf1ea
• Corpus ID: 235409722

High-resolution Laboratory Measurements of K-shell X-Ray Line Polarization and Excitation Cross Sections in Helium-like S XV Ions

@article{Shah2021HighresolutionLM,
  title={High-resolution Laboratory Measurements of K-shell X-Ray Line Polarization and Excitation Cross Sections in Helium-like S XV Ions},
  author={Chintan Shah and Natalie Hell and Antonia Hubbard and Ming Feng Gu and Michael J. MacDonald and Megan E. Eckart and Richard Lloyd Kelley and Caroline A. Kilbourne and Maurice A. Leutenegger and Frederick S. Porter and Gregory V. Brown},
  journal={The Astrophysical Journal},
  year={2021},
  volume={914}
}

• C. Shah, N. Hell, +8 authors Gregory V. Brown
• Published 11 June 2021
• Physics
• The Astrophysical Journal

We report measurements of electron-impact excitation cross sections for the strong K-shell n = 2 → 1 transitions in S xv, using the LLNL EBIT-I electron beam ion trap, two crystal spectrometers, and the EBIT Calorimeter Spectrometer. The cross sections are determined by direct normalization to the well-known cross sections of radiative electron capture, measured simultaneously. Using contemporaneous polarization measurements with the two crystal spectrometers, whose dispersion planes are oriented parallel and perpendicular to the electron beam direction, the polarization of the direct excitation line emission is determined, and in turn the isotropic total cross sections are extracted. We further experimentally investigate various line-formation mechanisms, finding that radiative cascades and collisional inner-shell ionization dominate the degree of linear polarization and total line-emission cross sections of the forbidden line, z.