Electronically stimulated adsorbate dissociation in the presence of an electronegative coadsorbate: (NO sub 2 +O) on Pt(111)

Journal Article · Wed Apr 15 00:00:00 EDT 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.8679· OSTI ID:7109808

Orlando, T M; Burns, A R; Jennison, D R; Stechel, E B ^[1]

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1. Sandia National Laboratories, Division 1151, Albuquerque, New Mexico 87185 (United States)

The effects of an electronegative coadsorbate on the stimulated dissociation of a chemisorbed molecule are investigated using state-resolved laser-ionization spectroscopy of those dissociation fragments which leave the surface. Specifically, we examine the NO({sup 2}{Pi}{sub {Omega}=1/2,3/2}) and O({sup 3}{ital P}{sub {ital J}}) fragment energies and yields resulting from electron- (6--350 eV) stimulated dissociation of chemisorbed NO{sub 2} as a function of preadsorbed atomic O coverage. The most dramatic effect associated with O coverage (up to {Theta}{sub O}=0.75 monolayer) is a large (a factor of 26) enhancement in the specific NO{sub 2} dissociation yield. There is also an O-induced narrowing of the translational energy distributions and a decrease in both the rotational and vibrational energy of the NO fragment. The dissociation threshold of {similar to}10 eV, together with lifetime arguments, suggest that the dominant excitation(s) are shallow-valence two-hole excitations. The above observations can be understood in terms of reduced substrate charge-transfer screening of these excitations. In addition, we observe a distinct propensity ({gt}4:1 at low {ital J}) for populating the upper ({Omega}=3/2) over the lower ({Omega}=1/2) level of the spin-orbit-split NO({sup 2}{Pi}{sub {Omega}}) ground state, whereas the spin-orbit population of the O({sup 3}{ital P}{sub {ital J}}) fragment is statistical (2{ital J}+1) within experimental error. The O({sup 3}{ital P}{sub {ital J}}) yield derives from dissociation of nitro-bound NO{sub 2} (N end down); no O({sup 3}{ital P}{sub {ital J}}) yield can be associated with side-bonded NO{sub 2}.

• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7109808
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 45:15; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
NITROGEN OXIDES
CHEMISORPTION
DISSOCIATION HEAT
OXYGEN
PLATINUM
SORPTIVE PROPERTIES
EPITAXY
HYBRIDIZATION
PHOTOELECTRON SPECTROSCOPY
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTRON SPECTROSCOPY
ELEMENTS
ENTHALPY
METALS
NITROGEN COMPOUNDS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM METALS
REACTION HEAT
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
400500* - Photochemistry