  We construct a measure for the adiabatic contribution to quantum transitions
in an arbitrary basis, tackling the generic complex case where dynamics is only
partially adiabatic, simultaneously populates several eigenstates and
transitions between non-eigenstates are of key interest. Our measure is
designed to distinguish transitions between basis states that occur due to the
adiabatic change of the underlying populated eigenstates from transitions that
occur due to beating between several such eigenstates. We demonstrate that the
measure can be applied to material or molecular simulations using
time-dependent density functional theory, allowing to quantify the relative
importance of adiabaticity and thus nuclear motion, for example, in charge or
energy transfer.
