J. Phys. B: At. Mol. Opt. Phys. 33 (2000) L859–L863. Printed in the UK PII: S0953-4075(00)50571-9 LETTER TO THE EDITOR Inner-shell photoexcited resonances in atomic oxygen T W Gorczyca† and B M McLaughlin‡ † Department of Physics, Western Michigan University, Kalamazoo, MI 49008-5151, USA ‡ Department of Applied Mathematics and Theoretical Physics, The Queen’s University of Belfast, Belfast BT7 1NN, UK Received 14 April 2000, in final form 3 November 2000 Abstract. Photoionization of atomic oxygen near the 1s -1 threshold is reinvestigated by including a more extensive inner-shell configuration interaction description, and by using an optical potential to account for autoionization to the infinite number of singly excited O + continua. These new theoretical results remove the earlier discrepancies between theory and experiment. An accurate description of the photoionization of oxygen is important for a number of atmospheric and astrophysical applications. This has been discussed in detail by McLaughlin and Kirby (1998) (hereafter referred to as paper I). In particular, with the recent launch of the x-ray satellites Chandra and XMM Newton and in the coming decade the launch of Constellation-X, the need for accurate theoretical photoabsorption cross section data is paramount. In paper I, the earlier valence shell work of Bell and co-workers (1989) was extended to treat the photoionization processes near the 1s -1 threshold. For valence shell photoionization of atomic oxygen, these extended wavefunctions produced results in suitable harmony with recent measurements performed by Wilhelmi et al (1999). For the inner-shell photoionization processes, while there was good overall qualitative agreement between the theoretical results of McLaughlin and Kirby (1998) and the experimental results of Stolte et al (1997) and those of Menzel et al (1996), significant discrepancies were apparent, mostly for the positions of the inner-shell excited resonances and the near-threshold resonance profiles. In this Letter, we readdress the main features of photoionization processes in the vicinity of inner-shell thresholds by focusing on the description of inner-shell excited states, and on their subsequent Auger decay. Near the 1s -1 thresholds of atomic oxygen, single-configuration considerations help to reveal the more important physical processes. Following inner-shell photoexcitation of the atomic oxygen ground state, hν + 1s 2 2s 2 2p 4 → 1s2s 2 2p 4 np, (1) there are two competing decay routes. First, there is participator Auger decay 1s2s 2 2p 4 np → 1s 2 2s 2 2p 3 +e - → 1s 2 2s2p 4 +e - , (2) where the valence electron np takes part in the autoionization process; the decay rate therefore scales as 1/n 3 . More importantly, there is spectator Auger decay 1s2s 2 2p 4 np → 1s 2 2s 2 2p 2 np+e - → 1s 2 2s2p 3 np+e - → 1s 2 2p 4 np+e - , (3) 0953-4075/00/240859+05$30.00 © 2000 IOP Publishing Ltd L859