Kastirke, GregorSchöffler, Markus S.Weller, MiriamRist, JonasBoll, RebeccaAnders, NilsBaumann, Thomas M.Eckart, SebastianErk, BenjaminDe Fanis, AlbertoFehre, KilianGatton, AverellGrundmann, SvenGrychtol, PatrikHartung, AlexanderHofmann, MaxIlchen, MarkusJanke, ChristianKircher, MaxKunitski, MaksimLi, XiangMazza, TommasoMelzer, NiklasMontano, JacoboMusic, ValerijaNalin, GiammarcoOvcharenko, YevheniyPier, AndreasRennhack, NilsRivas, Daniel E.Dörner, ReinhardRolles, DanielRudenko, ArtemSchmidt, PhilippSiebert, JulianeStrenger, NicoTrabert, DanielVela-Perez, IsabelWagner, ReneWeber, ThorstenWilliams, Joshua B.Ziolkowski, PawelSchmidt, Lothar Ph. H.Czasch, AchimUeda, KiyoshiTrinter, FlorianMeyer, MichaelDemekhin, Philipp V.Jahnke, Till2023-12-072023-12-072020-10-14https://hdl.handle.net/2097/44072We 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 O2 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.Creative Commons Attribution 4.0 International licensehttps://creativecommons.org/licenses/by/4.0/Text