ZF10 by CDGM

$$n(\lambda) = \sqrt{2.75929 - 0.00920456\,\lambda^2 + 0.0293164\,\lambda^{-2} + 0.00148741\,\lambda^{-4} - 7.05223 \times 10^{-5}\,\lambda^{-6} + 9.95388 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.02 \times 10^{-6} + 2(3.02 \times 10^{-8})\,\Delta T + 3(-2.4 \times 10^{-10})\,\Delta T^2 + \frac{1.33 \times 10^{-6} + 2(-1.33 \times 10^{-10})\,\Delta T}{\lambda - 0.247}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$