High Precision {\it K}-Shell Photoabsorption Cross Sections for Atomic Oxygen: Experiment and Theory

Abstract

Photoabsorption of atomic oxygen in the energy region below the $1{\mathrm{s}}^{-1}$ threshold in x-ray spectroscopy from {\it Chandra} and {\it XMM-Newton} is observed in a variety of x-ray binary spectra. Photoabsorption cross sections determined from an R-matrix method with pseudo-states (RMPS) and new, high precision measurements from the Advanced Light Source (ALS) are presented. High-resolution spectroscopy with E/$\Delta$E $\approx$ 4,250 $\pm$ 400 was obtained for photon energies from 520 eV to 555 eV at an energy resolution of 124 $\pm$ 12 meV FWHM. {\it K}-shell photoabsorption cross-section measurements were made with a re-analysis of previous experimental data on atomic oxygen at the ALS. Natural linewidths $\Gamma$ are extracted for the $1{\mathrm{s}}^{-1}2{\mathrm{s}}^{2}2{\mathrm{p}}^4{(}^4\mathrm{P})\mathrm{n}{\mathrm{p}}^3{\mathrm{P}}^{\circ }$ and $1{\mathrm{s}}^{-1}2{\mathrm{s}}^{2}2{\mathrm{p}}^4{(}^2\mathrm{P})\mathrm{np}{}^3{\mathrm{P}}^{\circ }$ Rydberg resonances series and compared with theoretical predictions. Accurate cross sections and linewidths are obtained for applications in x-ray astronomy. Excellent agreement between theory and the ALS measurements is shown which will have profound implications for the modelling of x-ray spectra and spectral diagnostics.

Accepted for publication in Ap J Letters; 4 figures and a table

References in corpus (1)

• Updated Atomic Data and Calculations for X-ray Spectroscopy

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