Guinier plot
A diagrammatic representation of data on scattering from large particles, obtained at different angles but at the same concentration, constructed by plotting log 10 Δ R θ or log 10 P θ versus (sin θ2)2 or q 2 and (usually) used for the evaluation of the radius of gyration. ΔRθ is the excess Rayleigh ratio, P θ the particle scattering function, θ the scattering angle and q the length of the scattering vector.
Purple Book, 1st ed., p. 67 (