  The removal of electrons located in the core shells of molecules creates
transient states that live between a few femtoseconds to attoseconds. Owing to
these short lifetimes, time-resolved studies of these states are challenging
and complex molecular dynamics driven solely by electronic correlation are
difficult to observe. Here, few-femtosecond core-excited state lifetimes of
iodine monochloride are obtained by attosecond transient absorption on iodine
4d-16p transitions around 55 eV. Core-level ligand field splitting allows
direct access of excited states aligned along and perpendicular to the ICl
molecular axis. Lifetimes of 3.5 fs and 4.3 fs are obtained for core-hole
states parallel to the bond and 6.5 fs and 6.9 fs for perpendicular states,
while nuclear motion is essentially frozen on this timescale. Theory shows that
the dramatic decrease of lifetime for core-vacancies parallel to the covalent
bond is a manifestation of non-local interactions with the neighboring Cl atom
of ICl.
