Reactivity of aluminum cluster anions with ammonia: Selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -}

Journal Article · Sat Nov 14 00:00:00 EST 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3256236· OSTI ID:21559803

Grubisic, Andrej; Xiang, Li; Gantefoer, Gerd; Bowen, Kit H ^[1]; Schnoeckel, Hansgeorg ^[2]; Tenorio, Francisco J ^[3]; Martinez, Ana ^[4]

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1. Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
2. Institut fuer Anorganische Chemie, Karlsruhe Universitaet, Karlsruhe 76128 (Germany)
3. Departamento de Ciencias Exactas y Tecnologia, Centro Universitario de Los Lagos, Universidad de Guadalajara, Jalisco 47460 (Mexico)
4. Departamento de Materia Condensada y Criogenia, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Coyoacan 04510, Distrito Federal (Mexico)

Reactivity of aluminum cluster anions toward ammonia was studied via mass spectrometry. Highly selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -} was observed at low concentrations of ammonia. However, at sufficiently high concentrations of ammonia, all other sizes of aluminum cluster anions, except for Al{sub 13}{sup -}, were also observed to deplete. The disappearance of Al{sub 11}{sup -} and Al{sub 12}{sup -} was accompanied by concurrent production of Al{sub 11}NH{sub 3}{sup -} and Al{sub 12}NH{sub 3}{sup -} species, respectively. Theoretical simulations of the photoelectron spectrum of Al{sub 11}NH{sub 3}{sup -} showed conclusively that its ammonia moiety is chemisorbed without dissociation, although in the case of Al{sub 12}NH{sub 3}{sup -}, dissociation of the ammonia moiety could not be excluded. Moreover, since differences in calculated Al{sub n}{sup -}+NH{sub 3} (n=9-12) reaction energies were not able to explain the observed selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -}, we concluded that thermodynamics plays only a minor role in determining the observed reactivity pattern, and that kinetics is the more influential factor. In particular, the conversion from the physisorbed Al{sub n}{sup -}(NH{sub 3}) to chemisorbed Al{sub n}NH{sub 3}{sup -} species is proposed as the likely rate-limiting step.

• OSTI ID: 21559803
• Journal Information: Journal of Chemical Physics, Vol. 131, Issue 18; Other Information: DOI: 10.1063/1.3256236; (c) 2009 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
74 ATOMIC AND MOLECULAR PHYSICS
ADSORPTION
ALUMINIUM
ALUMINIUM COMPOUNDS
AMMONIA
ANIONS
ATOMIC CLUSTERS
CHEMICAL ANALYSIS
CHEMISORPTION
DISSOCIATION
ETCHING
ION-MOLECULE COLLISIONS
MASS SPECTROSCOPY
MOLECULAR CLUSTERS
PHOTOELECTRON SPECTROSCOPY
REACTION KINETICS
REACTIVITY
SIMULATION
THERMODYNAMICS
CHARGED PARTICLES
CHEMICAL REACTIONS
COLLISIONS
ELECTRON SPECTROSCOPY
ELEMENTS
HYDRIDES
HYDROGEN COMPOUNDS
ION COLLISIONS
IONS
KINETICS
METALS
MOLECULE COLLISIONS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
SURFACE FINISHING