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Experimental and theoretical studies in large, ionized helium clusters have suggested the presence of structures in which a diatomic (and occasionally triatomic) charged molecular core is surrounded by nearly neutral atoms which are bound to it by weaker forces. The understanding of the interactions between the He2 + system and one of the neutral He atoms of the cluster is therefore crucial in order to understand the microscopic dynamics of the post-ionization evolution. The first part of this work [Eur. Phys. J. D21, 323 (2002)] reported the Potential Energy Surface (PES) for the interaction between the He2 + and an He atom and described its bound states. Since dynamical calculations require a more extensive variable range of the relevant PES to be sampled, we present here a further, more detailed study in which we span a larger configurational space for the three internal coordinates of the title system. In particular, we have included a greater range of internuclear distances of the molecular ion. The resulting ab initio values have been numerically fitted via an analytic expression in terms of the three internuclear distances within the He3 + system. As a first step in the analysis of the dynamics we have calculated the vibrational coupling terms which involve the ionic core vibrational wave functions and the interaction of the latter molecule with the external helium atom. They reveal interesting features and properties that are here discussed. [ABSTRACT FROM AUTHOR]

When a pure4He droplet is ionized by electron impact, the most abundant fragment detected in mass spectra after ionization is He2 +. All the models that have been proposed thus far to explain the experimental evidence therefore involve the formation of the He2 + molecular ion. The understanding of the interactions between this ion and the surrounding He atoms in the cluster and of their dynamical behavior during cluster break-up is an important element for the modeling of the cluster evolution after the ionization event. In previous works [1,2] we have computed and described the Potential Energy Surface (PES) of the electronic ground state for the He3 + system that provides the required forces between He2 + and He. After ionization He2 + is presumably formed by association of an He + and any of the neutral atoms in the cluster via a 3-body collision process. The ensuing vibrational quenching of the “hot” molecular ion may release the energy necessary to evaporate the entire droplet, or most of it, and give the fragmentation patterns detected by experiments. We present here a model quantum dynamics that generates vibrational deexcitation cross-sections and the corresponding rate coefficients for the collision of He2 + with He. A timescale of the cluster evaporation due to vibrational relaxation is estimated and the present findings are compared with earlier studies on the same system. [ABSTRACT FROM AUTHOR]