  The tiny-core generalized (Gatchina) relativistic pseudopotential (GRPP)
model provides an accurate approximation for many-electron Hamiltonians of
molecules containing heavy atoms, ensuring a proper description of the effects
of non-Coulombian electron-electron interactions, electronic self-energy and
vacuum polarization. Combining this model with electron correlation treatment
in the frames of the intermediate Hamiltonian Fock space coupled cluster theory
employing incomplete main model spaces, one obtains a reliable and economical
tool for excited state modeling. The performance of this method is assessed in
applications to \textit{ab initio} modeling of excited electronic states of the
thorium monoxide molecule with term energies below 20000 cm$^{-1}$. Radiative
lifetimes of excited states are estimated using truncated expansions of
effective and metric operators in powers of cluster amplitudes.
