Emission of singly and doubly charged light fragments fromC60r+(r=4

Abstract

Asymmetrical fission of C 60 rϩ (rϭ4 -9) ions are studied in Xe 25ϩ -C 60 collisions at 100 keV impact energy (vϷ0.18 a.u.). The branching ratios for the emission of a singly or a doubly charged light fragment, C m ϩ or C m 2ϩ , are measured for each initial charge state r. The measured m-dependent branching ratios for the singly charged C m ϩ fragment emission channels are reproduced using a simple statistical model. The ionization energies I(C 60Ϫ2n qϩ ) for even numbered fullerenes C 60Ϫ2n qϩ (qϭ1 -5, 8; nϭ1 -4) and I(C 2n ϩ ) for singly charged light fragments C 2n ϩ (nϭ1 -4) are estimated by the density-functional theory. The total branching ratio for the C m 2ϩ emission channels is found to increase from less than 2 to 25% when the charge r of the parent ion C 60 rϩ increases from 5 to 9.

Multiple ionization and fragmentation of isolated pyrene and coronene molecules in collision with ions

“…In the case of anthracene and pyrene molecules, it is found that the pericondensed form (pyrene) is more stable in kilo-electron volt ion-PAH collisions. To shed further light on the intriguing stability issues of (multiply) ionized PAHs, multicoincidence experiments similar to the ones for ion-fullerene collision [37,38,41,51] and high-level calculations of fission barriers [42] are needed. Further model developments in which the actual PAH molecular structures are taken into account would be useful.…”

“…Recent high-level calculations show that pyrene and coronene are thermodynamically unstable for charge states exceeding 3 and 4, respectively [36]. However, as in the case of C 60 fullerenes [37][38][39][40][41][42], fission barriers should prevent even more highly charged species from prompt decay. The present experiments show that C 16 expected for C 24 H 5+ 12 a small feature is present.…”

Stability and delayed fragmentation of highly charged C60 trapped in a conic-electrode electrostatic ion resonator (ConeTrap)

“…In our previous works, delayed asymmetric fission processes have been observed for C 4þ 60 and C 5þ 60 recoil ions [14,30]. Concerning evaporation processes, since our experimental set-up does not allow the detection of neutral fragments, it had not been possible to determine the lifetimes associated to these processes by analyzing coincidence spectra between fragments.…”

“…Andersen et al [28] have shown for C À 60 that when the internal energy is lower than 40 eV the cooling rate is greater than the dissociation rate. In our case, we have estimated the decay rates fission processes for C rþ 60 (r = 4-6) with the Arrhenius formula [29] in which the fission barriers have been set according to [30]. The calculated rates are displayed as a function of the excitation energy in Fig.…”

The Theoretical Study of Multiple Ionization of C60 Fullerene by Fast Proton Impact

“…Recently a number of the experimental data were published on the ionization and fragmentation of C 60 fullerenes under the ion bombardment. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] According to the experimental data, the C 2 evaporation is known as a preferential mechanism in the fragmentation of a fullerene, which accompanies the electron excitation and/or the plasmon excitation. The electron excitation (or, emission) by a charged particle is closely related to the electronic stopping power, while the phonon excitation is due to the nuclear stopping power.…”