TAFD35 by Hoya

$$n(\lambda) = \sqrt{3.52747 - 0.0148399\,\lambda^2 + 0.0397454\,\lambda^{-2} + 0.00180347\,\lambda^{-4} - 8.92793 \times 10^{-5}\,\lambda^{-6} + 1.13778 \times 10^{-5}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.96 \times 10^{-6} + 2(1.04 \times 10^{-8})\,\Delta T + 3(-2.57 \times 10^{-11})\,\Delta T^2 + \frac{8.88 \times 10^{-7} + 2(9.73 \times 10^{-10})\,\Delta T}{\lambda - 0.239}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$