This paper reports the experimental observation of a resonant double-core excitation scheme in N2, where two 1σ core-level electrons are resonantly promoted to unoccupied 1πg molecular orbitals by a single few-femtosecond broad-bandwidth XFEL pulse. The production of these neutral two-site double core hole states is evidenced through their characteristic decay channels, observed in agreement with theoretical calculations. Such multi-core excitation schemes, benefiting from high interaction cross sections and state- and site-selectivity, should be generally accessible in XFEL-irradiated molecules, offering opportunities for chemical analysis and monitoring ultrafast dynamic processes.

Eetu Pelimanni, Adam E. A. Fouda, Phay J. Ho, Thomas M. Baumann, Sergey I. Bokarev, Alberto De Fanis, Simon Dold, Gilbert Grell, Iyas Ismail, Dimitrios Koulentianos, Tommaso Mazza, Michael Meyer, Maria-Novella Piancastelli, Ralph Püttner, Daniel E. Rivas, Björn Senfftleben, Marc Simon, Linda Young, Gilles Doumy