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Free keywords:
Physics, Atomic Physics, physics.atom-ph, Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract:
We demonstrate a widely applicable technique to absolutely calibrate the
energy scale of x-ray spectra with experimentally well-known and accurately
calculable transitions of highly charged ions, allowing us to measure the
K-shell Rydberg spectrum of molecular O$_2$ with 8 meV uncertainty. We reveal a
systematic $\sim$450 meV shift from previous literature values, and settle an
extraordinary discrepancy between astrophysical and laboratory measurements of
neutral atomic oxygen, the latter being calibrated against the aforementioned
O$_2$ literature values. Because of the widespread use of such, now deprecated,
references, our method impacts on many branches of x-ray absorption
spectroscopy. Moreover, it potentially reduces absolute uncertainties there to
below the meV level.
