S-LAH79 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{2.32557\,\lambda^2}{\lambda^2 - 0.0132895} + \frac{0.507967\,\lambda^2}{\lambda^2 - 0.0528335} + \frac{2.43087\,\lambda^2}{\lambda^2 - 161.122}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[6.01 \times 10^{-6} + 2(1.31 \times 10^{-8})\,\Delta T + 3(-3.15 \times 10^{-11})\,\Delta T^2 + \frac{1.12 \times 10^{-6} + 2(1.27 \times 10^{-9})\,\Delta T}{\lambda - 0.26}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$