IOP PUBLISHING JOURNAL OF PHYSICS B: ATOMIC, MOLECULAR AND OPTICAL PHYSICS J. Phys. B: At. Mol. Opt. Phys. 46 (2013) 145002 (6pp) doi:10.1088/0953-4075/46/14/145002 Auger energies, branching ratios, widths and x-ray rates of double K -vacancy states of Ne 2+ : a close-coupling calculation Yanpeng Liu, Jiaolong Zeng and Jianmin Yuan Department of Physics, College of Science, National University of Defense Technology, 410073 Changsha Hunan, People’s Republic of China E-mail: jiaolongzeng@hotmail.com Received 1 May 2013, in final form 6 June 2013 Published 27 June 2013 Online at stacks.iop.org/JPhysB/46/145002 Abstract A close-coupling calculation is performed for the photoionization cross section of the high-lying core-excited state 1s2s 2 2p 51 P o of Ne 2+ in the energy region of the double K-vacancy resonance 1s 0 2s 2 2p 61 S. The calculation is carried out by using the R-matrix method in the LS-coupling scheme, which includes 27 target states and extensive configuration interaction. The KK−KL x-ray energy, rate and autoionization width of the double K-vacancy state, together with KK−KLL Auger energies and branching ratios of the main channels, are obtained from the cross sections and the contributions of these channels. The calculated resonance energy and x-ray rate are in good agreement with the existing experimental and theoretical results. For the Auger width, our result agrees well with the available experimental result and it is very close to the average of other theoretical data, which shows considerable differences with each other. The Auger energy of the predominate channel KK−KL 23 L 23 2 D is in rather good agreement with recent experiments on the Auger spectra. Our branching ratios for the channels KK−KL 23 L 23 2 D and KK−KL 23 L 23 2 S are larger than the results obtained by the multi-configuration Dirac–Fock method by ∼20% on average, which may be due to the coupling of the continuum channels. 1. Introduction The characteristics of the double K-vacancy states, known as hollow atoms, have always attracted attention. The newly arisen x-ray free-electron lasers (XFELs) providing very intense femtosecond x-ray pulses were used to investigate the atomic inner-shell processes [1–4]. The production of the hollow states with an XFEL such as the linac coherent light source is accessible since the sequential single-photon absorption became the dominant mechanism [3]. This is quite different from the energetic electrons’ impact [5, 6] and the double photoionization of the K-shell by absorbing a single photon of the x-ray synchrotron radiation [7, 8]. For low- Z atoms such as neon, the double K-vacancy states mainly decay by Auger transitions and can be observed by recording KK−KLL Auger electron spectra [3, 5–7]. So the Auger properties including energies, widths and branching ratios are important in modelling the interaction of intense x-ray lasers with atoms, molecules and clusters [9] and in modelling the radiative properties of local thermodynamic equilibrium (LTE) and non-LTE plasmas [10–14]. In addition, Auger rates and branching ratios also play an important role in the investigations of the double Auger decay and the cascade decay from inner-shell vacancy states [15–18]. The Auger transitions of an autoionizing state are entirely due to the electron–electron interactions, and strictly correlated with the coupling of the discrete state and the continuum channels. The close-coupling approximation was used to obtain the properties of the single K-vacancy resonances for atoms and ions such as B I [19], O I [20], Ne I [21], Al VII [22], Ne VII [23], Fe XV [24] and the double K-vacancy resonances for atomic lithium which has three electrons [25–27]. To our knowledge, few close-coupling calculations were reported for more complex systems with more than three electrons such as 1s 0 2s 2 2p 6 1 S of Ne 2+ . Some theoretical results were obtained by employing the multi-configuration Dirac–Fock (MCDF) method [6, 28, 29] in the Hartree–Fock (HF) model [30, 31], and some results were obtained in 0953-4075/13/145002+06$33.00 1 © 2013 IOP Publishing Ltd Printed in the UK & the USA