ORIENTATIONAL ORDERING OF A 2D MOLECULAR GAS

How does a molecule behave in a two-dimensional (2D) gas? We present a n analysis of the angular distributions obtained in resonance electron scattering by submonolayer films of O-2 physisorbed on graphite, whic h are able to distinguish between molecules adsorbed in the co-existin g solid and gas phases. The scattering analysis shows that molecules i n the 2D gas phase are preferentially oriented with their axes paralle l to the substrate. (C) 1997 Elsevier Science B.V.