H-ZF73GT by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.528337\,\lambda^2}{\lambda^2 - 0.0759306} + \frac{2.0596\,\lambda^2}{\lambda^2 - 0.0171346} + \frac{3.58638\,\lambda^2}{\lambda^2 - 189.365}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.47 \times 10^{-6} + 2(1.75 \times 10^{-8})\,\Delta T + 3(-4.65 \times 10^{-11})\,\Delta T^2 + \frac{1.29 \times 10^{-6} + 2(1.86 \times 10^{-9})\,\Delta T}{\lambda - 0.328}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$