The present simulations use the Langevin thermostat to regulate temperature (Section 2.1). With this method, a given temperature can be modeled by larger random forces ("kicks") and a larger drag coefficient, or by smaller kicks and a smaller drag coefficient. This scaling is controlled by the collision frequency parameter, which is connected with the viscosity. In the simulations described above, we used a collision frequency of 0.2/ps, so that the kinetic energy released during photoisomerization dissipates into the bulk solvent on a several picosecond timescale, in agreement with experimental observations for a related photoexcited system . For completeness, however, we also explored larger and smaller values of this parameter.