H 11 (q) λ 12 (q) λ 13 (q) λ 14 (q) λ 12 (q) H 22 (q) λ 23 (q) λ 24 (q) λ 13 (q) λ 23 (q) H 33 (q) λ 34 (q) λ 14 (q) λ 24 (q) λ 34 (q) H 44 (q)     (39) The analytical expression for the matrix elements in the model is summarized in appendix A 3. The normal modes are 6 modes of A symmetry (q 18 , q 20 , q 21 , q 24 , q 25 , q 26 ) and 2 modes of A symmetry (q 10 , q 12 ) within the uracil C s point group. Modes q 25 and q 26 correspond to the two C=O stretches, mode q 24 correspond to the C=C stretch, modes q 18 , q 20 and q 21 contain CN stretch and NCH/CNH bending motions and q 10 and q 12 are out of plane motions. This system, after photoionization to the D 2 excited cationic state, undergoes relaxation to the ground state before fragmentation involving ultrafast dynamics through a ) N tr = 400 trajectories are run starting in a pure state where each trajectory has initial populations ρ (α) D 0 = 0.01, ρ (α) D 1 = 0.05 and ρ (α) D 2 = 0.94. The initial electronic state used in the MCTDH reference is a pure state at each nuclear configuration, so this is likely a more accurate representation of the initial electronic state, however, with the assumption that the initial coefficients are real. It has an important effect on the dynamics: the quantum momentum is active from the start, in a region where the wavepackets overlap. The time-step used in the calculations is 0.25 fs for SH-EDC and 0.001 fs (0.04 /Ha) for the coupled-trajectory schemes. The initial conditions for the nuclear trajectories are obtained via Wigner sampling of the neutral uracil ground state (S 0 ) at the equilibrium geometry with variances obtained from the frequencies of the eight modes in the model.