  Multi-configuration range-separated density-functional theory is extended to
the time-dependent regime. An exact variational formulation is derived. The
approximation, which consists in combining a long-range
Multi-Configuration-Self-Consistent Field (MCSCF) treatment with an adiabatic
short-range density-functional (DFT) description, is then considered. The
resulting time-dependent multi-configuration short-range DFT (TD-MC-srDFT)
model is applied to the calculation of singlet excitation energies in H2, Be
and ferrocene, considering both short-range local density (srLDA) and
generalized gradient (srGGA) approximations. In contrast to regular TD-DFT,
TD-MC-srDFT can describe double excitations. As expected, when modeling
long-range interactions with the MCSCF model instead of the adiabatic
Buijse-Baerends density-matrix functional as recently proposed by Pernal [K.
Pernal, J. Chem. Phys. 136, 184105 (2012)], the description of both the 1^1D
doubly-excited state in Be and the 1^1\Sigma^+_u state in the stretched H2
molecule are improved, although the latter is still significantly
underestimated. Exploratory TD-MC-srDFT/GGA calculations for ferrocene yield in
general excitation energies at least as good as TD-DFT/CAM-B3LYP, and superior
to wave-function (TD-MCSCF, symmetry adapted cluster-configuration interaction)
and TD-DFT results based on LDA, GGA, and hybrid functionals.
