  We study the ultrafast time evolution of cyclobutanone excited to singlet
n-->Rydberg state through XMS-CASPT2 nonadiabatic surface-hopping simulations.
These dynamics predict relaxation to ground-state with a timescale of 822 +/-
45 fs with minimal involvement of triplets. The major relaxation path to the
ground-state involves a three-state degeneracy region and leads to variety of
fragmented photoproducts. We simulate the resulting time-resolved
electron-diffraction spectra which track the relaxation of the excited state
and the formation of various photoproducts in the ground-state.
