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ABSTRACT: We present a set of theoretical methods to study the different processes taking place in ion-fullerene collisions. In particular, we focus on charge transfer, excitation and fragmentation processes. These methods have been successfully applied to the case of He2+ + C60 collisions. We have found that single and double charge transfer cross sections are of the same order of magnitude in the velocity range studied (impact energy ~ 0.1 – 10 keV). Fragmentation of C+60 into C+58 + C2 is observed only with large excitation energies and/or if one waits long enough (detecting the fragments at large distances from the collision). The agreement between our predictions and the experimental results supports the validity of the methods presented.
Journal of Physics Conference Series 12/2009; 194(1):012047.
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A Rentenier, L F Ruiz,
S Díaz-Tendero,
B Zarour,
P Moretto-Capelle,
D Bordenave-Montesquieu,
A Bordenave-Montesquieu,
P-A Hervieux,
M Alcamí,
M F Politis,
J Hanssen,
F Martín
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ABSTRACT: We have determined absolute charge transfer and fragmentation cross sections in He2++C60 collisions in the impact-energy range 0.1-250 keV by using a combined experimental and theoretical approach. We have found that the cross sections for the formation of He+ and He0 are comparable in magnitude, which cannot be explained by the sole contribution of pure single and double electron capture but also by contribution of transfer-ionization processes that are important even at low impact energies. The results show that multifragmentation is important only at impact energies larger than 40 keV; at lower energies, sequential C2 evaporation is the dominant process.
Physical Review Letters 05/2008; 100(18):183401. · 7.37 Impact Factor
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ABSTRACT: We present a theoretical study of the dissociative
charge transfer processes induced by collisions between
doubly-charged alkaline clusters and alkaline atoms at slow and
intermediate impact energies. Charge-exchange cross sections have
been evaluated for the collisions of Li31
2+ and
Na31
2+ clusters with neutral alkaline atoms (Cs and Na)
at impact energies between 500 and 4000eV. The branching ratios
of the evaporation processes have been calculated within the
framework of the microcanonical statistical theory of Weisskopf.
The key ingredient of this model is the cluster vibrational
density of states. An approach based on quantum tight-binding
Hamiltonian is introduced, allowing us to evaluate this quantity at
a microscopic level, including quantum vibrational effects at low
temperatures. Comparison with previously reported results obtained
using a macroscopic description of the level density are presented
and discussed.
The European Physical Journal D 08/2007; 44(3):525-532. · 1.48 Impact Factor
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ABSTRACT: We present a combined theoretical and experimental study of dissociative charge transfer in collisions of slow Li312+ clusters with Cs atoms. We provide a direct quantitative comparison between theory and experiment and show that good agreement is only found when the experimental time-of-flight and initial cluster temperature are taken into account in the theoretical modeling. This model explains evaporation as resulting from a collisional energy deposit due to cluster electronic excitation during charge transfer. We discuss in detail the basic mechanisms that are responsible for the charge-transfer reaction and different approximations to evaluate the energy deposit.
Phys. Rev. A. 12/2003; 68(6).
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ABSTRACT: We present a combined theoretical and experimental study of charge transfer and dissociation in collisions of slow Li31(2+) clusters with Cs atoms. We provide a direct quantitative comparison between theory and experiment and show that good agreement is found only when the exact experimental time of flight and initial cluster temperature are taken into account in the theoretical modeling. We demonstrate the validity of the simple physical image that consists in explaining evaporation as resulting from a collisional energy deposit due to cluster electronic excitation during charge transfer.
Physical Review Letters 11/2002; 89(18):183402. · 7.37 Impact Factor
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ABSTRACT: We present a theoretical study of charge transfer in H++C60 and He2++C60 collisions using an extension of the molecular time-dependent method of ion–atom collisions. Energy-correlation diagrams have been evaluated for the corresponding (C60–H)+ and (C60–He)2+ quasi-molecules. Single and double charge-transfer cross sections in C60+He2+ collisions are reported for the first time. The results show that double charge-transfer cross sections are only one order of magnitude smaller than single charge-transfer cross sections. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
International Journal of Quantum Chemistry 08/2001; 86(1):106 - 113. · 1.36 Impact Factor
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Int. J. Quant. Chem. 86:106.
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ABSTRACT: We present charge transfer, excitation and evaporation cross sections in low energy collisions of small and medium-size metal clusters (Nanq+, Linq+) and C60 with atomic targets (H+, He2+ and Cs) using a molecular close-coupling formalism and a post-collision rate equation model. The theoretical model benefits from different time scales associated with the collision and the internal motion of the cluster nuclei. The collision description includes the many-electron aspect of the problem and makes use of a realistic cluster potential obtained with density functional theory and a spherical jellium model. The evaporation model takes into account the non-harmonic effects of the ionic motion and describes sequential evaporation to any order within the framework of the microcanonical statistical model of Weisskopf. We show that the relative abundance of different fragments depends critically on the cluster temperature and the spectrometer time of flight window. We have found good agreement with recent experimental results [Eur. Phys. J. D 12 (2000) 185].
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
