H-QF14 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.17413\,\lambda^2}{\lambda^2 - 119.559} + \frac{1.36038\,\lambda^2}{\lambda^2 - 0.00992936} + \frac{0.12524\,\lambda^2}{\lambda^2 - 0.0538484}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.82 \times 10^{-7} + 2(1.52 \times 10^{-8})\,\Delta T + 3(-3.21 \times 10^{-11})\,\Delta T^2 + \frac{6.73 \times 10^{-7} + 2(6.7 \times 10^{-10})\,\Delta T}{\lambda - 0.265}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$