Int. J. Mass Spect., 252, 126, 2006

DOI:10.1016/j.ijms.2005.12.055.

S. Díaz-Tendero, G. Sánchez, M. Alcamí, F. Martín, P.-A. Hervieux, M. Chabot, G. Martinet, P. Désesquelles F. Mezdari, KWohrer-Béroff, S. Della-Negra, H. Hamrita, A. LePadellec and L. Montagnon.

Fragmentation of small carbon clusters.

We report on theoretical and experimental efforts designed to understand the fragmentation of small neutral carbon clusters. Theoretically, the dissociation dynamics of Cn has been investigated using a statistical model based on the microcanonical Metropolis Monte Carlo method. In this model various structural quantities (geometries, dissociation energies, harmonic frequencies…) are required for both the parent cluster and the fragments. They have been obtained from quantum chemistry calculations for Cn up to n = 9. Experimentally, a new detection system for high velocity fragments has been recently developed allowing the fragmentation of high velocity clusters to be totally recorded. Results for the branching ratios of deexcitation of Cn with 5 ≤ n ≤ 9 formed by electron capture in high velocity Cn+–He collisions are presented. In all cases, the agreement between theory and experiment is reasonably good provided that the theoretical branching ratios are convoluted with a Cn energy distribution centered at around 10 eV.

Braz. J. Phys., 36B, 529, 2006

DOI:10.1590/S0103-97332006000400009.

S. Díaz-Tendero, G. Sánchez, P.-A. Hervieux, M. Alcamí, and F. Martín.

Ionization potentials, dissociation energies and statistical fragmentation of neutral and positively charged small carbon clusters. 

Dissociation energies, ionization potentials and fragmentation dynamics of neutral, singly- and doubly charged small carbon clusters have been theoretically studied with a combination of the density functional theory, the coupled cluster method and the the statistical model microcanonical Metropolis Monte Carlo. The second ionization potential decreases with the cluster size and is larger than the first one, which also decreases with the size showing oscillations. Dissociation energies also oscillate with the cluster size, being those with an odd number of atoms more stable. C3 cluster has the largest dissociation energy. The combination of a statistical treatment for the cluster fragmentation with experimental results has allowed us to evaluate the energy distribution in collisions experiments.

Int. J. Mass Spect., 252, 133, 2006

DOI:10.1016/j.ijms.2005.11.033

S. Díaz-Tendero, G. Sánchez, P.-A. Hervieux, M. Alcamí, and F. Martín

Ionization potentials and dissociation energies of neutral, singly and doubly charged Cn fullerenes from n=20-70.

Using B3LYP density functional theory, first and second ionization potentials as well as dissociation energies for neutral, singly and doubly charged fullerenes with sizes between 20 and 70 atoms have been evaluated. Comparison with available experimental data is good except for the doubly charged species. The results show that neutral fullerenes with a magic number of atoms, namely C32, C50, C60 and C70, have the largest stability against ionization and C2 evaporation. A similar large stability is observed for the corresponding singly and doubly charged magic fullerenes, except for C32+ and C322+. Neutral and positively charged C62 is found to be rather unstable. Also, C2+ emission is shown to become competitive with C2 emission for sufficiently small doubly charged fullerenes. The origin of these and other properties is discussed in detail.

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