Stabilities of multiply charged dimers and clusters of fullerenes

Abstract

The authors find even-odd variations as functions of r (<or=7) for multiple ionization of van der Waals dimers in slow Xe(30+)+[C60]2([C60C70])-->...+[C60]2(r+)([C60C70](r+)) electron-transfer collisions. This even-odd behavior is in sharp contrast to the smooth one for fullerene monomers and may be related to even-odd effects in dimer ionization energies in agreement with results from an electrostatic model. The kinetic energy releases for dimer dissociations [predominantly yielding intact fullerenes [C60]2(r+)-->C60(r1+)+C60(r2+) in the same (r1=r2) or nearby (r1=r2+/-1) charge states] are found to be low in comparison with the corresponding model results indicating that internal excitations of the separating (intact) fullerenes are important. Experimental appearance sizes for the heavier clusters of fullerenes [C60]n(r+) (n>3 and r=2-5) compare well with predictions from a new nearest-neighbor model assuming that r unit charges in [C60]n(r+) are localized to r C60 molecules such that the Coulomb energy of the system is minimized. The system is then taken to be stable if (i) two (singly) charged C60 are not nearest neighbors and (ii) the r C60(+) molecules have binding energies to their neutral nearest neighbors which are larger than the repulsive energies for the (r-1) C60(+)-C60(+) pairs. Essential ingredients in the nearest-neighbor model are cluster geometries and the present results on dimer stabilities.

The interaction of He− with fullerenes

“…In the case of dications, our findings agree with those of Zettergren et al, 18 with the smallest observed (C 60 ) n 2+ ion corresponding to n = 5. However, more highly charged fullerene cluster cations can also be observed.…”

“…18,24 As identified above, only ions with n ≥ 5 are stable against Coulomb explosion for the dications. As expected, the threshold appearance sizes are larger for more highly charged clusters, as summarized in Table I.…”

Ionization and fragmentation of polycyclic aromatic hydrocarbon clusters in collisions with keV ions

“…The slopes of the I q+1 k>1 as functions of q decrease with increasing k, which means not only that larger clusters are more easily ionized but also that the cross section for multiple electron capture increases strongly in relation to the single-electron-capture cross section. A similar effect has been observed and accounted for by means of an electrostatic model [62] applied to experimental results for large clusters of fullerenes [63,64] and in particular to multiply ionized C 60 dimers [64,65]. The dashed lines in Fig.…”

Theoretical study of the stability of multiply charged C70 fullerenes

“…This allows us to discuss the existing experimental results regarding the competition between different decay pathways and to predict the Coulomb stability limit for C 70 q+ . In addition, the present study provides accurate parameters that are important ingredients in simple electrostatic models used, e.g., to extract semiempirical fission barriers, 14,36 estimate electron transfer distances in fullerenefullerene collisions, 37 and for studies of the stabilities of fullerene dimers 38,39 and larger cluster of fullerenes. 39,40 The paper is organized as follows.…”