Wave packet model To describe the fragmentation of SF 6 in the core-excited state, we constructed a onedimensional wave packet model along the S-F bond R. Assuming the (F) 5 S moiety is rigid and fixed, the reduced mass will be given simply by the mass of the fluorine atom µ ≈ m F = 18.998 amu. The core-hole lifetime at the fluorine K-edge is 2Γ = 0.194 eV where Γ is the HWHM . Hence the nuclear Hamiltonian of the system on the i -th electronic state will be