Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray absorption via K-alpha resonance complexes in oxygen ions   The K-alpha resonance complexes in oxygen ions O I - O VI are theoretically
computed and resonance oscillator strengths and wavelengths are presented. The
highly resolved photoionization cross sections, with relativistic fine
structure, are computed in the coupled channel approximation using the
Breit-Pauli R-matrix method. A number of strong K-alpha resonances are found to
be appreciable, with resonance oscillator strengths f_r > 0.1. The K-alpha
resonance wavelengths of O I-O VI lie in a relatively narrow wavelength range
22 - 23.5 A, and the X-ray opacity in this region should therefore be
significantly affected by K --> L transitions in oxygen. The results should be
useful in the interpretation of soft X-ray spectra observed from Chandra and
XMM-Newton.

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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg