. The spawning threshold, which determines when the initial TBF reaches the coupling region (see Ref. for details on this parameter and others discussed in this paragraph), was set to 0.01 au -1 . Spawning occurred only when the overlap between one TBF in a given electronic state and any TBFs evolving on a different state dropped below 0.6. The nuclear momenta were rescaled along the nonadiabatic coupling vectors or along the nuclear momenta to conserve total energy between the parent and the child TBFs, depending on whether the norm of the nonadiabatic coupling vector is nonzero or not.