where the nonadiabatic coupling vector V m,s takes into account the electronic degrees of freedom, while nuclear quantum effects are taken into account via the experimental fitting parameters α ex and β ex . V m,s was calculated here based on an ab initio nonadiabatic model by Tapavicza and co-workers which casts the potential energy surface relevant to the transition in terms of the ground state. They also note that V m,s can be calculated using trajectory surface hopping , and directly substituted as the coupling term. Their resulting simulations found equal internal conversion rates of 7.55 × 10 7 s -1 for both L a and L b states. More rigorous methods are of course also available, such as factorised general coupled-trajectory model . However, despite this methods available detail, it remains highly laborious and computationally expensive.