H-ZF50 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.38419\,\lambda^2}{\lambda^2 - 121.21} + \frac{0.216863\,\lambda^2}{\lambda^2 - 0.0642534} + \frac{1.69855\,\lambda^2}{\lambda^2 - 0.0135196}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-4.21 \times 10^{-6} + 2(1.99 \times 10^{-8})\,\Delta T + 3(-3 \times 10^{-11})\,\Delta T^2 + \frac{8.92 \times 10^{-7} + 2(3.64 \times 10^{-10})\,\Delta T}{\lambda - 0.294}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$