These surface-hopping simulations used a Langevin thermostat targetting 90K, the temperature used in the relevant photoisomerization experiments , with a collision frequency of 0.2/ps. The Langevin thermostat provides a random "kick" to each atom at every time-step, to model solvent impacts, and a drag on each atom, proportional to its velocity, to model the effect of solvent viscosity. The balance of these energy-adding and damping forces effectively sets the target simulation temperature. We also tried the Nose-Hoover thermostat , an alternative to the Langevin thermostat, but this led to non-physical low-frequency kinetic energy oscillations not present in Langevin or constant energy simulations, even when a long Nose-Hoover chain was used, so we chose not to use this method.