The study investigates attosecond delays in x-ray molecular ionization, specifically focusing on core-level electron photoemission from nitric oxide (NO). Using attosecond x-ray pulses from a free-electron laser (XFEL), the researchers measured the time delay between electrons emitted from the oxygen and nitrogen $K$-shells. The measurements revealed unexpectedly large delays, up to 700 attoseconds, near the oxygen $K$-shell threshold. These delays are attributed to various factors, including transient trapping of the photoelectron due to shape resonances, collisions with the Auger-Meitner electron, and multi-electron scattering effects. The results demonstrate how x-ray attosecond experiments, combined with theoretical modeling, can provide insights into the complex correlated dynamics of core-level photoionization. The study also highlights the importance of electron correlation effects in accurately modeling the photoionization process.The study investigates attosecond delays in x-ray molecular ionization, specifically focusing on core-level electron photoemission from nitric oxide (NO). Using attosecond x-ray pulses from a free-electron laser (XFEL), the researchers measured the time delay between electrons emitted from the oxygen and nitrogen $K$-shells. The measurements revealed unexpectedly large delays, up to 700 attoseconds, near the oxygen $K$-shell threshold. These delays are attributed to various factors, including transient trapping of the photoelectron due to shape resonances, collisions with the Auger-Meitner electron, and multi-electron scattering effects. The results demonstrate how x-ray attosecond experiments, combined with theoretical modeling, can provide insights into the complex correlated dynamics of core-level photoionization. The study also highlights the importance of electron correlation effects in accurately modeling the photoionization process.