K-shell dielectronic resonances in photoabsorption:: Differential oscillator strengths for Li-like CIV, OVI, and Fe XXIV -: art. no. 060701

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 er at, Astrophys. J. Lett. (to be published)]. The required resonance oscillator strengths (f) over bar (r) are evaluated in terms of the differential oscillator strength df/d epsilon that relates bound and continuum absorption. We present the (f) over bar (r) values from radiatively damped and undamped photoionization cross sections for Li-like C, O, and Fe calculated using relativistic the close-coupling Breit-Pauli R-matrix method. The KLL resonances of interest here are 1s2p(P-3(o))2s [P-4(1/2,3/2)o P-2(1/2,3/2)o] and 1s2p(P-1(o))2s [P-2(1/2,3/2)o]. The KLL photoabsorption resonances in Fe XXIV are fully resolved up to natural autoionization profiles. It is demonstrated that the undamped (f) over bar (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 (f) over bar (r). The dielectronic satellites may appear as redward broadening of resonance lines in emission and absorption.