K-shell dielectronic resonances in photoabsorption: Differential oscillator strengths for Li-like C IV, O VI, and Fe XXIV
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Publisher:American Physical Society
Citation:Nahar, Sultana Nurun, Pradhan, Anil K., Zhang, Hong Lin. "K-shell dielectronic resonances in photoabsorption: Differential oscillator strengths for Li-like C IV, O VI, and Fe XXIV," Physical Review A Rapid Communications, v. 63, no. 6, 2001.
Recently x-ray photoabsorption in KLL resonances of O VI was predicted [A. K. Pradhan, Astrophys. J. Lett. 545, L165 (2000)], and detected by the Chandra X-Xay Observatory [J. C. Lee et al., Astrophys. J. Lett. (to be published)]. The required resonance oscillator strengths ƒ¯_r are evaluated in terms of the differential oscillator strength df/dε that relates bound and continuum absorption. We present the ƒ¯_r values from radiatively damped and undamped photoionization cross sections for Li-like C, O, and Fe calculated using relativistic close-coupling Breit-Pauli R-matrix method. The KLL resonances of interest here are 1s2p(^3 P°)2s [^4 P°_1/2,3/2, ^2 P°_1/2,3/2] and 1s2p(^1 P°)2s [^2 P°_1/2,3/2]. The KLL photoabsorption resonances in Fe XXIV are fully resolved up to natural autoionization profiles. It is demonstrated that the undamped ƒ¯_r independently yield the resonance radiative decay rates, and thereby provide a precise check on the resolution of photoionization calculations in general. The predicted photoabsorption features should be detectable by the x-ray space observatories and enable column densities in highly ionized astrophysical plasmas to be determined from the calculated ƒ¯_r . The dielectronic satellites may appear as redward broadening of resonance lines in emission and absorption.
Relevant data is available at: http://www.astronomy.ohio-state.edu/~nahar/nahar_radiativeatomicdata/index.html
This work was partially supported by the National Science Foundation and the NASA Astrophysical Theory Program.