Evaporation of covalent clusters: Unimolecular decay of energized size-selected carbon cluster ions (Cn+, 5=n=100)


Por: Radi P.P., Hsu M.T., Brodbelt-Lustig J., Rincon M., Bowers M.T.

Publicada: 1 ene 1990
Resumen:
The unimolecular decay of energized size-selected carbon clusters (C n+,5 ? n ? 100) is investigated. The clusters are produced in a laser-generated plasma on the surface of a graphite rod. Directly extracted cations that decay on a ?s time scale are probed in a double-focusing, reverse-geometry mass spectrometer. The unimolecular decomposition rates are extracted from metastable fraction measurements. We observe a dramatic discontinuous increase in the decay rate constant as a function of cluster size around mass C30+ (factor of 5 to 10). Additionally, low rate constants, relative to the neighbors, are found for C50+, C60+, and C70 +. The results are rationalized by postulating a phase transition from small "rigid" clusters for n < 30 to larger "molten" entities for n > 30. In this model local deviations in rate constant reflect the thermodynamic stabilities of the clusters. A further consequence of this model is that "magic" numbers in the mass spectrum originate primarily from the intrinsic stability of the clusters with respect to evaporation and not from a kinetic growth mechanism. © 1990 American Institute of Physics.

Filiaciones:
Radi P.P.:
 Department of Chemistry, University of California, Santa Barbara, CA 93106, United States

Hsu M.T.:
 Department of Chemistry, University of California, Santa Barbara, CA 93106, United States

Brodbelt-Lustig J.:
 Department of Chemistry, University of California, Santa Barbara, CA 93106, United States

Rincon M.:
 Department of Chemistry, University of California, Santa Barbara, CA 93106, United States

Bowers M.T.:
 Department of Chemistry, University of California, Santa Barbara, CA 93106, United States
ISSN: 00219606
Editorial
AMER INST PHYSICS, CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA, Estados Unidos America
Tipo de documento: Article
Volumen: 92 Número: 8
Páginas: 4817-4822
WOS Id: A1990DC48400021