H-ZF4A by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.67238\,\lambda^2}{\lambda^2 - 0.0133654} + \frac{1.34134\,\lambda^2}{\lambda^2 - 122.464} + \frac{0.204305\,\lambda^2}{\lambda^2 - 0.0641192}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-5.36 \times 10^{-6} + 2(1.47 \times 10^{-8})\,\Delta T + 3(-3.86 \times 10^{-11})\,\Delta T^2 + \frac{1.02 \times 10^{-6} + 2(8.24 \times 10^{-10})\,\Delta T}{\lambda - 0.276}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$