UBK7 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.01237\,\lambda^2}{\lambda^2 - 0.00588329} + \frac{0.258985\,\lambda^2}{\lambda^2 - 0.019024} + \frac{1.00022\,\lambda^2}{\lambda^2 - 104.08}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.7 \times 10^{-6} + 2(1.34 \times 10^{-8})\,\Delta T + 3(-1.26 \times 10^{-11})\,\Delta T^2 + \frac{4.42 \times 10^{-7} + 2(5.15 \times 10^{-10})\,\Delta T}{\lambda - 0.167}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$