In our simulations, we use up to N m = 23 modes with frequencies ω j (in cm -1 ) and dimensionless excited-state shifts c j /ω j (in parenthesis) from Ref. (lower panel) compares the adiabatic BO potential energies as functions of the variable ϕ for q = 0 considering only the system (in blue and red) and considering the system coupled to only 3 of the modes listed here (in orange and dark green), i.e., mode 1, 8 and 23, at an arbitrary choice of the bath positions