  We introduce a microscopic approach for calculating the excitation energies
of systems formed during heavy-ion collisions. The method is based on
time-dependent Hartree-Fock (TDHF) theory and allows the study of the
excitation energy as a function of time or ion-ion separation distance. We
discuss how this excitation energy is related to the estimate of the excitation
energy using the reaction $Q$-value, as well as its implications for dinuclear
pre-compound systems formed during heavy-ion collisions.
