H-TF8 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.60563\,\lambda^2}{\lambda^2 - 0.0103175} + \frac{1.32554\,\lambda^2}{\lambda^2 - 108.474} + \frac{0.265359\,\lambda^2}{\lambda^2 - 0.0488739}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.81 \times 10^{-7} + 2(1.7 \times 10^{-8})\,\Delta T + 3(-3.95 \times 10^{-11})\,\Delta T^2 + \frac{7.69 \times 10^{-7} + 2(5.75 \times 10^{-10})\,\Delta T}{\lambda - 0.256}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$