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arXiv · 1809.08455

Photoionization of metastable heliumlike C4+(1s 2s 3S1) ions: Precision study of intermediate doubly excited states

A. Müller·E. Lindroth·S. Bari·A. Borovik Jr.·P. -M. Hillenbrand·K. Holste·P. Indelicato·A. L. D. Kilcoyne·S. Klumpp·M. Martins·J. Viefhaus·P. Wilhelm·S. Schippers
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Abstract

In a joint experimental and theoretical endeavour, photoionization of metastable C4+(1s 2s 3S1) ions via intermediate levels with hollow, double-K-vacancy configurations 2s2p, 2s3p, 2p3s, 2p3d, 2s4p, 2p4s and 2p4d has been investigated. High-resolution photon-ion merged-beams measurements were carried out with the resolving power reaching up to 25,000 which is sufficient to separate the leading fine-structure components of the 2s2p 3P term. Many-body perturbation theory was employed to determine level-to-level cross sections for K-shell excitation with subsequent autoionization. The resonance energies were calculated with inclusion of electron correlation and radiative contributions. Their uncertainties are estimated to be below $\pm$1 meV. Detailed balance confirms the present photoionization cross-section results by comparison with previous dielectronic-recombination measurements. The high accuracy of the theoretical transition energies together with the present experimental results qualify photoabsorption resonances in heliumlike ions as new, greatly improved energy-reference standards at synchrotron radiation facilities.

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A. Müller, E. Lindroth, S. Bari, A. Borovik Jr., P. -M. Hillenbrand, K. Holste, P. Indelicato, A. L. D. Kilcoyne, S. Klumpp, M. Martins, J. Viefhaus, P. Wilhelm, S. Schippers. 2018-09-22. Photoionization of metastable heliumlike C4+(1s 2s 3S1) ions: Precision study of intermediate doubly excited states. https://doi.org/10.1103/physreva.98.033416

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