@staticmethod
def _fraction_freeStacked(r0, r_inf):
    """
        Calculate the fraction of free and stacked dyes based on the residual anisotropy

        Parameters
        ----------
        r0 : float
        r_inf : float

        Returns
        -------
        weights : tuple
                  fraction of free and stacked dye components
        """
    w_free = (r0 - r_inf) / r0
    w_stacked = 1 - w_free
    return w_free, w_stacked
