title: NO dimer and dinitrosyl formation on Pd(111): from ultra-high-vacuum to elevated pressure conditions.
abstract: Using in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and conventional IRAS techniques, the adsorption of NO on Pd(111) was studied from ultra-high-vacuum (UHV) conditions to 400 mbar. New monomeric and non-monomeric high-coverage NO adsorption states were observed at 400 mbar. Initial NO adsorption at 600 K and subsequent cooling in the presence of 400 mbar NO lead to a new high-coverage monomeric adsorption state. For NO adsorption at room temperature, the formation of NO dimer as well as dinitrosyl states was observed, which upon heating transformed into the high-coverage monomeric adsorption state. In contrast, under UHV conditions, NO dimers were stable only at low temperatures up to 60 K, above which they transformed into a monomeric NO adsorption state with a (2x2)-3NO structure. Our results demonstrate that stable NO dimeric and dinitrosyl species can be formed on Pd(111) at elevated pressure conditions, emphasizing their potential role in catalysis.
authors.affiliation: Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, TX 77842-3012, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Hess
authors.forename: Emrah
authors.initials: E
authors.lastname: Ozensoy
authors.forename: Cheol-Woo
authors.initials: CW
authors.lastname: Yi
authors.forename: D Wayne
authors.initials: DW
authors.lastname: Goodman