We resonantly excite the $K$ series of ${\mathrm{O}}^{5+}$ and ${\mathrm{O}}^{6+}$ up to principal quantum number $n=11$ with monochromatic x rays, producing $K$-shell holes, and observe their relaxation by soft-x-ray emission. Some photoabsorption resonances of ${\mathrm{O}}^{5+}$ reveal strong two-electron–one-photon (TEOP) transitions. We find that for the ${\left[{\left(1s2s\right)}_{1}5p_{3/2}\right]}_{3/2;1/2}$ states, TEOP relaxation is by far stronger than the radiative decay and competes with the usually much faster Auger decay path. This enhanced TEOP decay arises from a strong correlation with the near-degenerate upper states ${\left[{\left(1s2p_{3/2}\right)}_{1}4s\right]}_{3/2;1/2}$ of a Li-like satellite blend of the He-like $K\alpha$ transition. Even in three-electron systems, TEOP transitions can play a dominant role, and the present results should guide further research on the ubiquitous and abundant many-electron ions where electronic energy degeneracies are far more common and configuration mixing is stronger.

中文翻译：

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少数电子离子中的强二电子一光子跃迁的观察

我们共振地激发了 $ķ$ 系列 ${\mathrm{Ø}}^{5+}$ 和 ${\mathrm{Ø}}^{6+}$ 高达主量子数 $ñ=11$ 带有单色X射线，产生 $ķ$壳孔，并通过软X射线观察其松弛。的一些光吸收共振${\mathrm{Ø}}^{5+}$揭示了强大的两电子一光子（TEOP）跃迁。我们发现${\left[{（\mathrm{1个}s2s）}_{\mathrm{1个}}5p_{3/2}\right]}_{3/2;\mathrm{1个}/2}$据称，TEOP弛豫远比辐射衰减强，并且与通常更快的俄歇衰减路径竞争。增强的TEOP衰减源于与简并的上态的强烈相关性${\left[{（\mathrm{1个}s2p_{3/2}）}_{\mathrm{1个}}4s\right]}_{3/2;\mathrm{1个}/2}$ 像氦一样的锂像卫星混合物 $ķ\alpha$过渡。即使在三电子系统中，TEOP跃迁也可以起主导作用，目前的研究结果应指导对普遍存在的大量电子离子进行更深入的研究，其中电子能量简并性更强，构型混合更强。