Swift cluster-atom collisions: experiment and model calculations

Abstract

Single, double and triple ionization cross sections of 10 MeV projectiles colliding with He atoms have been measured. This was achieved thanks to a new experimental set-up allowing for a complete collection and unambiguous identification (in particular with respect to their charge) of all the fragments emitted by the dissociative species (Q = 2, 3, 4). As a first attempt to understand the mechanisms of ionization in the cluster we use these results, together with those we obtained in the identical velocity 2 MeV system, for testing the predictions of an {independent atoms} - atom collision calculation within the impact parameter formalism and using the independent-electron approximation. The model is found to be surprisingly good in predicting the cluster - atom results when appropriate (i.e. able to reproduce the atom - atom case) impact parameter dependent ionization probabilities are used.

Fragmentation branching ratios of highly excited hydrocarbon molecules CnH and their cations CnH+ (n⩽4)

“…The electronic excitation and ionization cross sections exhibit the same evolution with n. This trend is well reproduced by the Independent Atom and Electron (IAE) model 30,36 in the case of ionization. In the IAE calculations, shown by a broken line, classical trajectory Monte Carlo (CTMC) impact parameter probabilities P(b) were used for valence ionization in C and C + as in previous works 25,37 .…”

“…In the standard utilization of silicon solid state detectors, the charge delivered by the detector provides the kinetic energy of the fragment i.e its mass for fragments of constant velocity 30 . With this property and the (q/m) analysis, the charge of each fragment was recorded.…”

Unraveling the Metastability of Cn2+ (n = 2–4) Clusters

“…Díaz-Tendero et al reached the same conclusion by means of DFT and coupled-cluster (CC) theory simulations . Wohrer et al produced both long-lived and excited C 5 2+ ions by high-velocity collisions of 10 MeV C 5 + ions with a He target . They observed that conversely to metal cluster ions, whose dominant fission channels are those giving rise to almost symmetric fragments, the C 5 2+ ions mainly decay to C 4 + + C + .…”

“…31 Wohrer et al produced both long-lived and excited C 5 2+ ions by high-velocity collisions of 10 MeV C 5 + ions with a He target. 32 They observed that conversely to metal cluster ions, whose dominant fission channels are those giving rise to almost symmetric fragments, the C 5 2+ ions mainly decay to C 4 + + C + . 33 There is also experimental work reporting the detection of the C n 2+ ( n = 2–4) cluster ions using time-of-flight (TOF) mass spectroscopy, 34,35 but the stability and fragmentation dynamics of the clusters have not been explored in detail.…”

Coulomb Explosion of Polycyclic Aromatic Hydrocarbons Induced by Heavy Cosmic Rays: Carbon Chains Production Rates

“…Absolute cross sections are derived by integrating over b the IAE probabilities such as (1). Since individual b i 's depend not only on b but also on the grain orientation (Wohrer et al 1994(Wohrer et al , 1996, we average the calculation over all equally probable grain orientations (θ, ϕ in spherical coordinates) following equation ( 4)…”