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Low energy electrons and surface chemistry / G. Ertl, J. Küppers
Auteur:Ertl, Gerhard Contributeur:Küppers, Jürgen Edition:
2nd, completely rev. ed. Editeur:
Weinheim : VCH Verlag
XII, 374 p. : ill. ; 25 cm
Classification:LC QD506 Identifiant:
3527260560 (ISBN); http://catalogue.bnf.fr/ark:/12148/cb373531795 (URN) No RERO:
A TDS study of D adsorption on terraces and terrace edges of graphite (0 0 0 1) surfaces
Zecho, Thomas, Güttler, Andreas, Küppers, Jürgen
Carbon, 2004, Vol.42(3), pp.609-617
[Revue évaluée par les pairs]
ScienceDirect Journals (Elsevier)
Titre: Reactions of gas-phase H atoms with atomically and molecularly adsorbed oxygen on Pt(111) Auteur:Biener, Jürgen; Lang, Erwin; Lutterloh, Carsten; Küppers, Jürgen Sujet:Articles Description:
The interaction of gas-phase H atoms with ordered and disordered adlayers of atomic oxygen, hydroxyl, and molecular oxygen on Pt(111) surfaces was investigated by in situ mass spectrometry and post-reaction TPD (temperature programed desorption). Exposure of oxygen adlayers to gas-phase H atoms at 85 K leads to formation of H 2 O via two consecutive hydrogenation reactions: H (g)+ O (a)→ OH (a) followed by H (g)+ OH (a)→ H 2 O (g,a). Both reaction steps are highly exothermic, and nascent H 2 O molecules partially escape into the gas phase before being thermally accommodated on the surface. Empty surface sites and hydrogen bonding promote thermalization of H 2 O . Separate experiments performed with OH-covered Pt(111) surfaces reveal that the hydrogenation of hydroxyl is a slow reaction compared to the hydrogenation of atomic oxygen; additionally, the abstraction of H from OH by gas-phase D atoms, OH (a)+ D (g)→ O (a)+ HD (g), was detected. Abstraction of H from adsorbed H 2 O was not observed. Admission of gas-phase H atoms to O 2 -covered Pt(111) surfaces at 85 K leads to the desorption of O 2 and H 2 O . The thermodynamic stability of the HO 2 radical suggests that the reaction is initiated by hydrogenation of molecular oxygen, O 2 (a)+ H (g)→ HO 2 . The intermediate HO 2 either decomposes via dissociation of the HO–O bond, HO 2 → OH (a)+ O (a), finally leading to the formation of H 2 O (∼85%), or via dissociation of the H–O 2 bond thus leading to desorption of O 2 (∼15%). The whole reaction sequence of formation and decomposition of HO 2 is fast compared to the formation of H 2 O via hydrogenation of atomic oxygen and hydroxyl. The observed coverage dependence of the reaction kinetics indicates the dominance of hot-atom mediated reactions.
Fait partie de:
The Journal of Chemical Physics, 15 February 2002, Vol.116(7), pp.3063-3074
0021-9606 (ISSN); 1089-7690 (E-ISSN); 10.1063/1.1436075 (DOI)
Titre: Adsorption of hydrogen and deuterium atoms on the (0001) graphite surface Auteur:Zecho, Thomas; Güttler, Andreas; Sha, Xianwei; Jackson, Bret; Küppers, Jürgen Sujet:Articles Description:
Adsorption of H and D on HOPG surfaces was studied with thermal desorption (TDS), electronic (ELS), and high-resolution electron-energy-loss (HREELS) spectroscopies. After admission of H (D) from thermal (2000 K) atom sources to clean graphite surfaces TD spectra revealed recombinative molecular H 2 ( D 2 ) desorption in a main peak around 445 K (490 K) and a minor peak at 560 K (580 K). After admission of higher fluences the main peak shifts to 460 K (500 K) and develops a shoulder at 500 K (540 K). The saturation coverages were calculated as 0.4±0.2 for H and D and initial sticking coefficients of 0.4±0.2 were obtained. Through leading edge analysis of the TD spectra desorption activation energies for H and D were determined as 0.6 and 0.95 eV, respectively. EL spectra suggest a 16% loss of the sp 2 character of the surface carbon 2sp electrons upon D adsorption. HREEL spectra of H (D) graphite covered surfaces reveal in addition to two graphite-intrinsic optical phonon losses vibrational features at 1210 and 2650 cm −1 (and 640 and 1950 cm −1 ). These frequencies are in excellent agreement with those obtained from a recently published H (D)/graphite potential energy surface. A theoretical description of the desorption process through calculated H + H / graphite potential surfaces reveals the desorption mechanism and desorption activation energies which are in good agreement with the measured data.
Fait partie de:
The Journal of Chemical Physics, 08 November 2002, Vol.117(18), pp.8486-8492
0021-9606 (ISSN); 1089-7690 (E-ISSN); 10.1063/1.1511729 (DOI)
UHV Study of Hydrogen Atom Induced Etching of Amorphous Hydrogenated Silicon Thin Films
Zecho, Thomas, Brandner, Birgit D, Biener, Jürgen, Küppers, Jürgen
The journal of physical chemistry. B, 03 May 2001, Vol.105(17), pp.3502-3509
[Revue évaluée par les pairs]