H-BAF5 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.06905\,\lambda^2}{\lambda^2 - 112.004} + \frac{0.104158\,\lambda^2}{\lambda^2 - 0.0516104} + \frac{1.41844\,\lambda^2}{\lambda^2 - 0.00956493}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-7.5 \times 10^{-7} + 2(1.62 \times 10^{-8})\,\Delta T + 3(-3.14 \times 10^{-11})\,\Delta T^2 + \frac{6.63 \times 10^{-7} + 2(6.5 \times 10^{-10})\,\Delta T}{\lambda - 0.241}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$