Research Collaborations

C.R. Arumainayagam, E.C. Tripa, J. Xu, J.T. Yates, Jr., "IR Spectroscopy of Adsorbed Dinitrogen: A Probe of Defect Sites on Pt(111)," Surface Sci., 360 (1996) 121.more

Fourier transform IR reflection absorption spectroscopy (FT-IRAS) was used to probe the non-dissociative adsorption of N₂ on an atomically clean Pt(111) single crystal. In contradiction to a previous IRAS study of nitrogen adsorption on a Pt(111) foil at 120 K, no nitrogen IR (IR) band was obsd. on a fully annealed Pt(111) surface at 90 K. Following Ar⁺ ion bombardment, adsorption of nitrogen at 90 K produces an intense IR band at .apprx. 2222cm^-1 attributed to the N-N stretching mode of mol. nitrogen adsorbed on defect sites produced by ion bombardment. Annealing the Ar⁺ ion sputtered surface to a temp. above .apprx.750 K completely suppresses the adsorption of nitrogen at 90 K. Based on these and other results, it is postulated that nitrogen adsorbs at 90 K mainly on monovacancies on platinum. It is suggested that this specific adsorption occurs by sigma donation from nitrogen to the base of monovacancy sites which possess a low d-electron d. compared to surface Pt atoms.

C.E. Tripa, C.R. Arumainayagam, J.T. Yates, Jr., "Kinetics Measurements of CO Photoxidation on Pt(111)," J. Chem. Phys., 105 (1996) 1691.more

The photoactivation of chemisorbed O₂ in the presence of chemisorbed CO on Pt(111) has been investigated for uv light in the range 3.87–4.77 eV (260–320 nm). Three photoprocesses first-order in O₂ coverage have been separated and for the first time the cross sections for each are reported. The dominant process is O₂ photodissociation (Qdiss=4.0±0.1×10–21 cm²). The second most probable process is photodesorption (Qdes=2.2±0.1×10–21 cm²). The least probable process is photoreaction with chemisorbed CO (Qrxn=0.35±0.03×10–21 cm²). Previous studies of Qrxn have reported cross sections as high as 5×10–17 cm².

K.L. Queeney, C.R. Arumainayagam, M.K. Weldon, C.M. Friend, and M.Q. Blumberg,* "Differential Reactivity and Structure of Mono- and Di-alkoxides: the Reactions of Ethylene Glycol on Mo(110)," J. Am. Chem. Soc., 118 (1996) 3896. more

The reactions of ethylene glycol on Mo(110) were studied using temp.-programmed reaction, IR reflection absorption, and X-ray photoelectron spectroscopies. The major reaction pathway is double C-O bond scission to evolve gas-phase ethylene at 350 and 390 K. Both X-ray photoelectron and IR spectra demonstrate the existence of two surface intermediates, a bidentate (-OCH₂CH₂O-) and a monodentate (-OCH₂CH₂OH) species, at satn. coverage of ethylene glycol. We demonstrate that all ethylene glycol in the mixed overlayer of mono- and bidentate species reacts via a bidentate surface intermediate. Furthermore, in contrast to previous studies on other surfaces, the dialkoxide ethylene glycol intermediate is shown to be more reactive than similar monoalkoxides on Mo(110). Finally, anal. of the IR spectra demonstrates that the bidentate species adsorbs with C₂ (or lower) symmetry at 300 K.

K.T. Queeney, C.R. Arumainayagam, A. Balaji*, and C.M. Friend, "Carbon-Carbon Coupling from Formaldehyde Reaction on Mo(110)," Surface Sci., 418 (1998) L31-L38. more

Formaldehyde (CH₂O) reaction on Mo(110) is studied with temp. programmed reaction and IR reflectance absorbance spectroscopy. We present preliminary results which demonstrate the evolution of gas-phase ethylene from the formaldehyde reaction, to the best of our knowledge the first example of carbon-carbon bond formation on clean Mo(110). This reaction is proposed to proceed via an ethylene dialkoxide intermediate, analogous to that formed during reaction of ethylene glycol on Mo(110). Other reactions include hydrogenation of CH₂O to form a methoxy intermediate which subsequently undergoes C-O bond scission to evolve gas-phase Me radicals at .apprx.600 K.