def double_pnum(n, F1, alpha, comp1, kwargs1, comp2, kwargs2):
    u"""
    Double component models where the particle number is given in
    the model i.e. for confocal diffusion models.

    Parameters
    ----------
    n : float
        Total particle number
    F1 : float
        Fraction of particle species 1
    alpha : float
        Relative molecular brightness of particle
        2 compared to particle 1 (α = q₂/q₁)
    comp1, comp2 : callables
        The model functions for each of the components.
    kwargs1, kwargs2 : dicts
        The keyword arguments for `comp1` and `comp2`
    """
    norm = (F1 + alpha * (1 - F1)) ** 2
    g1 = F1 * comp1(**kwargs1)
    g2 = alpha ** 2 * (1 - F1) * comp2(**kwargs2)
    G = 1 / n * (g1 + g2) / norm
    return G
