hide
Free keywords:
Physics, Atomic Physics, physics.atom-ph, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE, Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM, Astrophysics, Solar and Stellar Astrophysics, astro-ph.SR, Physics, Plasma Physics, physics.plasm-ph
Abstract:
We measured the L-shell soft X-ray fluorescence of Fe XVII ions in an
electron beam ion trap following resonant photo-excitation using synchrotron
radiation provided by the P04 beamline at PETRA III. Special attention is paid
to two 2p-3d transitions, the 3C and 3D lines that are essential plasma
diagnostics tools for astrophysics. Their resulting oscillator-strength ratio,
f(3C)/f(3D) = 3.09(8)(6), is three times more accurate than previous results.
The present ratio clearly departs by approximately 5-sigmas from the newest ab
initio calculations but confirms previous laboratory measurements and
astrophysical observations. A ten thousand-fold reduction in excitation-photon
intensity and ten times higher spectral resolution allow us to exclude current
explanations, reinstating a forty-year-old atomic-physics puzzle.