The clean and hydrogenated Ge(113) surface was investigated using refl
ectance anisotropy spectroscopy (RAS). Surface-induced optical transit
ions related to the 3 x 2 reconstruction of the clean surface were ide
ntified. Two of these transitions are quenched when hydrogen adsorptio
n changes the reconstruction. With increasing temperature, the optical
transitions observed in the RAS spectra are shifted. At temperatures
above 1000 K the RAS signal drops in intensity due to surface melting.