H-BAF7 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.08754\,\lambda^2}{\lambda^2 - 117.536} + \frac{1.41618\,\lambda^2}{\lambda^2 - 0.0100875} + \frac{0.126987\,\lambda^2}{\lambda^2 - 0.0526007}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.13 \times 10^{-6} + 2(1.51 \times 10^{-8})\,\Delta T + 3(-4.77 \times 10^{-11})\,\Delta T^2 + \frac{7.49 \times 10^{-7} + 2(5.54 \times 10^{-10})\,\Delta T}{\lambda - 0.25}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$