We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate "rings" and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology.

We report the first experimental study of ions interacting with clusters of polycyclic aromatic hydrocarbon (PAH) molecules. Collisions between 11.25 keV 3He+ or 360 keV 129Xe20+ and weakly bound clusters of one of the smallest PAH molecules, anthracene, show that C14H10 clusters have much higher tendencies to fragment in ion collisions than other weakly bound clusters. The ionization is dominated by peripheral collisions in which the clusters, very surprisingly, are more strongly heated by Xe20+ collisions than by He+ collisions. The appearance size is k=15 for [C ₁₄H₁₀](k)2+.

International audienceThe interaction of multiply charged ions (He(2+), O(3+), and Xe(20+)) with gas-phase pericondensed polycyclic aromatic hydrocarbon (PAH) molecules of coronene (C(24)H(12)) and pyrene (C(16)H(10)) is studied for low-velocity collisions (v <= 0.6 a.u.). The mass spectrometric analysis shows that singly and up to quadruply charged intact molecules are important reaction products. The relative experimental yields are compared with the results of a simple classical over-the-barrier model. For higher molecular charge states, the experimental yields decrease much more strongly than the model predictions due to the instabilities of the multiply charged PAH molecules. Even-odd oscillations with the number of carbon atoms, n, in the intensity distributions of the C(n)H(x)(+) fragments indicate a linear chain structure of the fragments similar to those observed for ion-C(60) collisions. The latter oscillations are known to be due to dissociation energy differences between even-and odd-n C(n)-chain molecules. For PAH molecules, the average numbers of H atoms attached to the C(n)H(x) chains are larger for even-n reflecting acetylenic bond systems

We report highly selective covalent bond modifications in collisions between keV alpha particles and van der Waals clusters of C 60 fullerenes. Surprisingly, C 119 þ and C 118 þ are the dominant molecular fusion products. We use molecular dynamics simulations to show that C 59 þ and C 58 þ ions-effectively produced in prompt knockout processes with He 2þ -react rapidly with C 60 to form dumbbell C 119 þ and C 118 þ . Ion impact on molecular clusters in general is expected to lead to efficient secondary reactions of interest for astrophysics. These reactions are different from those induced by photons. DOI: 10.1103/PhysRevLett.110.185501 PACS numbers: 61.48.Àc, 31.15.xv, 36.40.Qv Photodriven intracluster reactions have been observed in clusters of fullerenes [1,2] and in, e.g., clusters of methanol, water, dimethyl ether, and acetic acid molecules [3]. Clusters of fullerenes are of particular interest in this context as C 60 and C 70 recently have been observed in space [4,5] at temperatures indicating that they may reside on grains [4] or are in the solid phase (fullerite) [6]. The question of how fullerenes form in space and elsewhere [7][8][9] is still open and here we report experimental observations on specific very efficient fullerene growth processes inside small pieces of fullerite material. These ion-impact induced growth processes in which so-called dumbbell fullerene systems are formed are inherently different from the ones induced by photons [1,2] for reasons that will be discussed in the following.The lowest energy barrier for formation of covalently bound dumbbell C 120 from two neutral C 60 molecules is roughly one or two electron volts [10]. Thus, two C 60 molecules in their ground states may, in principle, form such a C 120 system when the center-of-mass kinetic energy is larger than this barrier. However, molecular dynamics simulations by Jakowski, Irle, and Morokuma [11] have shown that, in practice, much larger kinetic energies are needed to form dumbbell C 120 (* 60 eV) or single-cage C 120 (*100 eV) efficiently [11]. The reason is that at least one C 60 cage needs to rearrange to form covalent bonds with the other cage on very short, picosecond, time scales. This is highly unlikely in a single encounter at low kinetic energy, as the transferred energy is redistributed over the fullerene molecule and a critical energy needs to be localized in a specific bond in order to break it. On the other hand, the reverse reaction (dissociation) may proceed at much lower energies but after many vibrations and on much longer time scales. For C 60 -C 60 collisions at kinetic energies above 60/100 eV covalent bond formation becomes much more likely but will then also give internally hot dumbbell/single-cage C 120 . Single-cage C 120 will fragment through sequences of C 2 emissions yielding molecular mass distributions with an even number of carbon atoms [1] as C 2 loss is the lowest-energy dissociation channel at about 10 eV. The dumbbell C 120 ! C 60 þ C 60 dissociation energy is only a couple of eV [1...