We report on a multiparticle coincidence experiment performed at the European X-ray Free-Electron Laser at the Small Quantum Systems instrument using a COLTRIMS reaction microscope. By measuring two ions and two electrons in coincidence, we investigate double core-hole generation in ${\mathrm{O}}_2$ molecules in the gas phase. Single-site and two-site double core holes have been identified and their molecular-frame electron angular distributions have been obtained for a breakup of the oxygen molecule into two doubly charged ions. The measured distributions are compared to results of calculations performed within the frozen- and relaxed-core Hartree-Fock approximations.

中文翻译：

---

使用X射线自由电子激光在O2分子中产生双核孔：分子框架光电子角分布

我们报告了在欧洲的X射线自由电子激光在小量子系统仪器上使用COLTRIMS反应显微镜进行的多粒子重合实验。通过同时测量两个离子和两个电子，我们研究了双核孔的产生${\mathrm{Ø}}_2$气相中的分子。已经确定了单中心和双中心双核空穴，并且已经获得了它们的分子框架电子角分布，以将氧分子分解为两个双电荷离子。将测得的分布与在冻结核和松弛核Hartree-Fock近似中执行的计算结果进行比较。