Optical Absorption in Vapor-Quenched Aluminum

An aluminum film formed by evaporation at 25 K onto a similar film previously deposited at room temperature displayed a featureless optical spectrum in the range 0.6-3.5 eV, the characteristic (200) peak being completely absent. A closer analysis showed the absorption to consist of a Drude term ($\hslash {\omega }_p=7.45\mathrm{}$ eV; $\tau =3.4\mathrm{}\times {10}^{-15\mathrm{}}$ sec) and what is believed to be interband absorption, possibly associated with a residual (111) absorption band.