H-BAF3 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.16102\,\lambda^2}{\lambda^2 - 0.00637009} + \frac{0.926012\,\lambda^2}{\lambda^2 - 107.342} + \frac{0.290936\,\lambda^2}{\lambda^2 - 0.0265573}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.14 \times 10^{-6} + 2(1.83 \times 10^{-8})\,\Delta T + 3(-3.7 \times 10^{-11})\,\Delta T^2 + \frac{5.37 \times 10^{-7} + 2(7.04 \times 10^{-10})\,\Delta T}{\lambda - 0.22}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$