Crossed beams studies of Mo(a S-7(3)) and Mo-*(a S-5(2)) collisions with CH4 and C2H6

The interactions of Mo(a S-7(3)) and Mo*(a S-5(2)) with methane, CH4, and e thane, C2H6, were studied under single collision conditions using the cross ed molecular beams technique. Ground state Mo(a S-7(3)) atoms were found to be unreactive at all collision energies studied up to [E-coll] = 35.4 kcal /mol. Nonreactive scattering of Mo(a S-7(3)) with methane and ethane was st udied and compared to collisions with Ne and Ar. A forward peaking center-o f-mass angular distribution, T(Theta), was necessary to simulate the elasti c collisions with inert gases as well as inelastic collisions with the alka nes. At a collision energy of 14.4 kcal/mol with CH4 and 21.0 kcal/mol with C2H6, inelastic collisions were found to transfer similar to 10% and simil ar to 19% of the initial kinetic energy into alkane internal energy, respec tively. For collisions of Mo*(a S-5(2)) + CH4, the dehydrogenation product, MoCH2, was observed at all collision energies studied down to 2.1 kcal/mol . The reaction Mo*(a S-5(2)) + C2H6--> MoC2H4 + H-2 was observed down to [E -coll] = 4.5 kcal/mol. For a given total energy (electronic+translational), it was found that electronic energy is highly effective in promoting this reaction whereas translational energy is ineffective. (C) 2000 American Ins titute of Physics. [S0021-9606(00)00910-7].