State-resolved measurements of CH4 and CHD3 dissociation on Ni (111)

State-resolved measurements of the dissociative chemisorption of methane on a Ni (111) surface are performed in an ultra-high vacuum (UHV) chamber using supersonic molecular beam methods and narrow-bandwidth continuous wave (CW) infrared (IR) laser excitation. Two detection methods are used in analyzing the amount of dissociative products on the nickel surface: O2 titration and bulk deuterium/hydrogen (D/H) temperature programmed desorption (TPD).;Thermally excited methane molecules have a certain level of translational energy as well as vibrational energy depending on the vibrational population of the molecules at that temperature. We perform a series of sticking probability measurements at a few fixed nozzle temperatures with a large translational energy range achieved by changing the gas mixture type and ratio. We analyze the results using error function and linear fit to generate the sticking probability curve for the ground vibrational state. This is the first time sticking probability of methane for the ground vibrational state on a 550 K Ni (111) surface is determined experimentally.;Bond and mode selective chemistry is studied by using deuterated methane molecules, CHD3, under nu1 laser excitation. Reactivity of CHD3 on a low temperature Ni (111) surface is measured systematically for the first time. Our results confirm a greater reactivity of C-H bond compared with the C-D bond. The laser-on results confirm that the excitation of C-H nu1 symmetric stretching mode promotes the cleavage of a C-H bond exclusively. The state-resolved sticking probability of CHD 3 on a 90 K Ni (111) surface shows a sharp energy threshold for the reaction, which is similar to the behavior of CH4 and CH2 D2 as indicated in the previous study in our group. When energy is localized on a C-H bond, similar reactivity is observed for nu 1 and nu3, which indicates the basis for nu1 and nu3 is more complicated than simply symmetry.;Using the bulk D TPD method, we measure the sticking probability of CH 4 on a 90 K Ni (111) surface with laser excitation at nu3 anti-symmetric stretch mode. The TPD results indicate higher sticking probability than former results obtained from O2 titration method. The difference of results between O2 titration, bulk D and bulk H TPD methods indicates a possible change of surface chemistry caused by bulk D or H.