Aluminium Reflectivity

The reflectivity of aluminium is well modelled by extending the Fresnel reflection coefficients to cover complex refractive indices; the theory of this is dealt with in most text books. The energy dependance of the refractive index has been experimentally investigated [13], and these values have been modelled with sixth order polynomials whose coefficients were derived from a least squares fit to the data between 2 and 6 eV. The coefficients are shown in Table 12.2. The RMS deviations from the fit are 0.99% and 0.13% for the real and imaginary parts of the refractive index respectively.

Table: Coefficients for the polynomials describing the aluminium refractive index $\tilde{n} = n+ik$.

Power	$P_n$	$P_k$
$x^0$	18.020	21.060
$x^1$	-22.208	-10.609
$x^2$	12.007	1.8587
$x^3$	-3.5144	0.2434
$x^4$	0.5795	-0.1467
$x^5$	-0.0507	0.0211
$x^6$	0.0018	0.0044