DYNAMICS OF THE FORMATION OF CD4 FROM THE DIRECT REACTION OF INCIDENTD-ATOM WITH CD3 CU(111)/

Using molecular beam techniques we find that incident D atoms can abst ract CD3 from a Cu(111) surface to yield CD4 in a direct (Eley-Rideal) gas-surface reaction with a cross section of similar to 10(-16) cm(2) /D atom. Dynamical evidence for a direct reaction includes the observa tion of an extremely sharp angular distribution that is clearly displa ced from the surface normal, and the determination of a very: high tra nslational energy of the product, E(f), which is similar to 2 eV. For a 0.25 eV D-atom beam incident at 45 degrees on a 95 K surface, this e nergy varies with the detection angle, theta(f), as E(f)(theta(f))=(1. 8+theta(f)/45) eV, where theta(f)<0 degrees in the ''backscattering'' direction. For these conditions, the angular distribution approximatel y follows the function cos(70)(theta(f)-5.5), being peaked 5.5 degrees from the normal with a full width at half maximum of <17 degrees. Low ering the beam energy to 0.07 eV gives a broader angular distribution peaked at about 1.5 degrees from the normal, consistent with cos(60)(t heta(f)-1.5). The reaction with 0.25 eV H incident at 45 degrees gives a similar distribution peaked at similar to 3.5 degrees from the norm al. The shifts in the angular distributions are approximately consiste nt with parallel momentum conservation. The CD3/Cu(111) surface was pr epared by thermal dissociation of CD3I on the surface or by adsorbing CD3 directly from a CD3 beam produced by the pyrolysis of azomethane. (C) 1996 American Institute of Physics.