Direct observation of scaling by high-resolution low-energy electron diffraction: O on Mo(110)

The critical behavior of the order-disorder transition in the (2×2) lattice of oxygen on the (110) molybdenum surface is studied by low-energy electron diffractometry with a coherence length of about 600 Å. The critical exponents η, γ, ν, and β of a system which belongs to the universality class of the XY model with cubic anisotropy are extracted for the first time by a new method based on the general scaling properties of the correlation function. η is found to be abnormally large for T>$T_c$ and T dependent, approaching the value 0.25 for T→$T_c$. γ, ν, and β have the (T independent) values 1.20±0.10, 0.84±0.07, and 0.19±0.02, respectively.