TAFD32 by Hoya

$$n(\lambda) = \sqrt{3.39611 - 0.0130871\,\lambda^2 + 0.0348535\,\lambda^{-2} + 0.000790832\,\lambda^{-4} + 7.69952 \times 10^{-6}\,\lambda^{-6} + 2.35167 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.82 \times 10^{-7} + 2(8.11 \times 10^{-9})\,\Delta T + 3(-2.84 \times 10^{-11})\,\Delta T^2 + \frac{9.6 \times 10^{-7} + 2(9.61 \times 10^{-10})\,\Delta T}{\lambda - 0.141}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$