One-dimensional diffusion coefficients ${\overline{D}}_{L_z}$ (top panel) and ${\overline{D}}_{L_z{L}_z}$ (bottom panel) of equations (K.5), computed for the rotating isotropic clusters with α​ = ​0.25, and with the smoothing parameters a​ = ​1, 5, 10, 15, ∞, as defined in equation (K.2). These coefficients are well-defined for all values of L_z. In addition, they only (very) weakly depend on a, with relative differences of order 1–5%.