Fragmentation Dynamics Research Articles

Experimental determination of fragment dynamics of refractory non-metallic silicate material under high-velocity impact

The individual velocity of rupture fragments after impact is necessary to evaluate how dangerous they are after dispersion. The aim of the study is to experimentally determine the velocity of rupture fragments upon impact on a refractory non-metallic silicate material (potassium fluorophlogopite). The targets made from potassium fluorophlogopite were shaped in the form of flat plates with a size of 280x160x15 mm. A steel ball with a diameter of 23 mm was used as a projectile. Four impact experiments were performed with the following parameters: ball speed of 230 m/s and collision angle of 90°; ball speed of 120 m/s and collision angle of 90°; ball speed of 230 m/s and collision angle of 30°; ball speed of 120 m/s and collision angle of 30°. The velocity of the rupture fragments was determined through video recording obtained using a high-speed Photron Fastcam SA5 camera. The video was processed by analyzing frame-by-frame images using the ImageJ-FiJi. The velocities of individual rupture fragments upon impact on a refractory non-metallic silicate material are experimentally determined using the example of potassium fluorophlogopite. It is established that the nature of the change in the fragment velocity relative to time corresponds to a hyperbolic function and depends on the kinetic energy of the fragments. A coefficient for calculating the change in the velocity of rupture fragments of potassium fluorophlogopite relative to time is proposed.

Disentangling sequential and concerted fragmentations of molecular polycations with covariant native frame analysis.

We present results from an experimental ion imaging study into the fragmentation dynamics of 1-iodopropane and 2-iodopropane following interaction with extreme ultraviolet intense femtosecond laser pulses with a photon energy of 95 eV. Using covariance imaging analysis, a range of observed fragmentation pathways of the resulting polycations can be isolated and interrogated in detail at relatively high ion count rates (∼12 ions shot-1). By incorporating the recently developed native frames analysis approach into the three-dimensional covariance imaging procedure, contributions from three-body concerted and sequential fragmentation mechanisms can be isolated. The angular distribution of the fragment ions is much more complex than in previously reported studies for triatomic polycations, and differs substantially between the two isomeric species. With support of simple simulations of the dissociation channels of interest, detailed physical insights into the fragmentation dynamics are obtained, including how the initial dissociation step in a sequential mechanism influences rovibrational dynamics in the metastable intermediate ion and how signatures of this nuclear motion manifest in the measured signals.

Fragmentation dynamics of CH3Clq+ (q = 2,3): theory and experiment.

A combined theoretical and experimental study of the dissociation of the di- and trication of the CH3Cl molecule has been performed. Experimentally, these multi-charged ions were produced after interactions of a CH3Cl effusive jet with a mono-energetic beam of H+ or Ar9+ projectile ions. Theoretically, we mapped the multi-dimensional potential energy surfaces of CH3Cl2+, H2CClH2+ and CH3Cl3+ species in their electronic ground and electronically excited states using post-Hartree-Fock configuration interaction methods. In addition to the obvious bond-breaking ionic fragments (i.e. H+ + CH2Cl+, H+ + CH2Cl2+ and CH3+ + Cl+), the formation of H2+ (+CHCl+ or CHCl2+), H3+ (+CCl+) and HCl+ (+CH2+) was observed upon bond rearrangement after ion impact of CH3Cl. The interaction strength of the incident projectiles is found to affect the relative yields on the observed dissociation channels, however, it has no effect on the kinetic energy releases of the fragmentation pathways. For the observed dissociation channels, plausible formation mechanisms were proposed. These reaction pathways take place on the ground and/or electronic excited potential energy surfaces of the doubly and triply charged CH3Cl ions, where spin-orbit and vibronic couplings are in action. Moreover, this work suggests that the mechanisms undertaken may depend on the multiply charged ion preparation by valence or inner-shell single photon photoionization, fast ion beam impact or ultrafast intense laser ionization.

A recoil ion momentum spectrometer for probing ionization, e-capture, and capture-ionization induced molecular fragmentation dynamics.

The development of a recoil ion momentum spectrometer (RIMS) along with a post-collision projectile charge state analyzer (CSA) and its performance for carrying out studies of molecular fragmentation following direct ionization, electron-capture, and capture-ionization have been demonstrated here. This is a two-stage Wiley-McLaren type spectrometer with slight modification introduced by adding a lens to achieve higher momentum resolution as well as larger angular acceptance. Along with the time and position sensitive detector, it can measure all the three momentum components of singly charged recoil ions of energy up to 10 eV emitted in all directions. The CSA assembly is designed for separating out any neutral or singly or doubly charged post-collision projectiles typically of keV energy. The RIMS with initial trigger ("start") from CSA or an ionized electron can uniquely determine the dynamics of molecular fragmentation following different electron-capture or direct ionization events, respectively. To check the performance of the setup, we carried out an experimental study of the fragmentation of N2 molecules under the impact of 250 keV protons. Apart from the single-electron-capture channel, we could clearly identify three more capture-ionization channels, which lead to fragmentation. The essential features of the momentum distributions and the kinetic energy release distributions of all three fragmentation channels are discussed in detail. These results are compared with the findings from the ionization induced fragmentation experiments and with the available results from theoretical calculations as well as high resolution experiments. The branching ratios of these fragmentation channels are determined.

ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – V. Hierarchical fragmentation and gas dynamics in IRDC G034.43+00.24

ABSTRACT We present new 3-mm continuum and molecular lines observations from the ATOMS survey towards the massive protostellar clump, MM1, located in the filamentary infrared dark cloud (IRDC), G034.43+00.24 (G34). The lines observed are the tracers of either dense gas (e.g. HCO+/H13CO+ J= 1–0) or outflows (e.g. CS J= 2–1). The most complete picture to date of seven cores in MM1 is revealed by dust continuum emission. These cores are found to be gravitationally bound, with virial parameter, αvir < 2. At least four outflows are identified in MM1 with a total outflowing mass of ∼45 M⊙, and a total energy of 1 × 1047 erg, typical of outflows from a B0-type star. Evidence of hierarchical fragmentation, where turbulence dominates over thermal pressure, is observed at both the cloud and the clump scales. This could be linked to the scale-dependent, dynamical mass inflow/accretion on clump and core scales. We therefore suggest that the G34 cloud could be undergoing a dynamical mass inflow/accretion process linked to the multiscale fragmentation, which leads to the sequential formation of fragments of the initial cloud, clumps, and ultimately dense cores, the sites of star formation.

Charging and ion ejection dynamics of large helium nanodroplets exposed to intense femtosecond soft X-ray pulses

Ion ejection from charged helium nanodroplets exposed to intense femtosecond soft X-ray pulses is studied by single-pulse ion time-of-flight (TOF) spectroscopy in coincidence with small-angle X-ray scattering. Scattering images encode the droplet size and absolute photon flux incident on each droplet, while ion TOF spectra are used to determine the maximum ion kinetic energy, \(E_{\text {kin}}\), of \(\hbox {He}_{j}^{+}\) fragments (j = 1–4). Measurements span \(\hbox {He}_N\) droplet sizes between \(N\sim 10^{7}\) and \(\sim 10^{10}\) (radii \(R_0\) = 78–578 nm), and droplet charges between \(\sim 9\times 10^{-5}\) and \(\sim 3\times 10^{-3}\) e/atom. Conditions encompass a wide range of ionization and expansion regimes, from departure of all photoelectrons from the droplet, leading to pure Coulomb explosion, to substantial electron trapping by the electrostatic potential of the charged droplet, indicating the onset of hydrodynamic expansion. The unique combination of absolute X-ray intensities, droplet sizes, and ion \(E_{\text {kin}}\) on an event-by-event basis reveals a detailed picture of the correlations between the ionization conditions and the ejection dynamics of the ionic fragments. The maximum \(E_{\text {kin}}\) of He\(^{+}\) is found to be governed by Coulomb repulsion from unscreened cations across all expansion regimes. The impact of ion-atom interactions resulting from the relatively low charge densities is increasingly relevant with less electron trapping. The findings are consistent with the emergence of a charged spherical shell around a quasineutral plasma core as the degree of ionization increases. The results demonstrate a complex relationship between measured ion \(E_{\text {kin}}\) and droplet ionization conditions that can only be disentangled through the use of coincident single-pulse TOF and scattering data.

Statistical analysis of correlations in the x-ray induced Coulomb explosion of iodopyridine

Coulomb explosion imaging is a promising experimental tool to study individual molecules. In this work simulation data for the x-ray induced Coulomb explosion of 2-iodopyridine is analyzed and the involved fragmentation dynamics are described. It is found that particular final ion momenta show correlations that reflect a collision of two atoms during the explosion. Variations of the proton kinetic energies can be associated with variations in the charge build-up time. Covariances of the forces during the explosion can be utilized to simplify the description of the dynamics in reduced dimensionality using only four collective coordinates.

Integrable spin chain with Hilbert space fragmentation and solvable real-time dynamics.

We revisit the so-called folded XXZ model, which was treated earlier by two independent research groups. We argue that this spin-1/2 chain is one of the simplest quantum integrable models, yet it has quite remarkable physical properties. The particles have constant scattering lengths, which leads to a simple treatment of the exact spectrum and the dynamics of the system. The Hilbert space of the model is fragmented, leading to exponentially large degeneracies in the spectrum, such that the exponent depends on the particle content of a given state. We provide an alternative derivation of the Hamiltonian and the conserved charges of the model, including an alternative interpretation of the so-called "dual model" considered earlier. We also construct a nonlocal map that connects the model with the Maassarani-Mathieu spin chain, also known as the SU(3) XX model. We consider the exact solution of the model with periodic and open boundary conditions, and also derive multiple descriptions of the exact thermodynamics of the model. We consider quantum quenches of different types. In one class of problems the dynamics can be treated relatively easily: we compute an example for the real-time dependence of a local observable. In another class of quenches the degeneracies of the model lead to the breakdown of equilibration, and we argue that they can lead to persistent oscillations. We also discuss connections with the TT[over ¯] and hard rod deformations known from quantum field theories.

Zero-point averaged dynamics of Arn+He1000: Dopant-size influence on potential-energy surfaces, mass spectra and fragmentation patterns

• Effective He-He potentials are little sensitive to the dopant embedded in HNDs. • No Ar + He q fragments detected for Ar n + He 1000 clusters ( n = 3 - 5 ) . • Fast ion ejections, ion trappings, and geminate recombinations for all Ar n + He 1000 . • Inefficient relaxation of Ar 3 + initially excited in its uppermost electronic state. The fragmentation of Ar n + He 1000 ( n = 3 , 5 ) is investigated by zero-point averaged dynamics (ZPAD) and compared with recent results on Ar 4 + He 1000 to investigate the influence of the dopant size. At the core of ZPAD, effective He-He potentials converged for He 1000 and Ar n He 1000 are found alike which suggests that ZPAD simulations on argon-doped helium nanodroplets (HNDs) could restrict to effective potentials obtained for pure HNDs. The fragmentation dynamics of Ar n + He 1000 clusters share a number of similarities, like the absence of Ar + -containing fragments, the occurrence of ion ejections and trappings, Ar n + electronic relaxation typically extending on a picosecond time scale, or primary fragmentation events which are not necessarily representative of the final distribution of fragments. However, Ar 3 + He 1000 clusters also exhibit unexpected behaviors like an inefficient electronic relaxation when the dynamics starts on the uppermost Ar 3 + electronic state which makes the dopant trapped within the droplet.

Ab Initio Direct Dynamics.

The reactivity and dynamics of molecular systems can be explored computationally by classical trajectory calculations. The traditional approach involves fitting a functional form of a potential energy surface (PES) to the energies from a large number of electronic structure calculations and then integrating numerous trajectories on this fitted PES to model the molecular dynamics. The ever-decreasing cost of computing and continuing advances in computational chemistry software have made it possible to use electronic structure calculations directly in molecular dynamics simulations without first having to construct a fitted PES. In this "on-the-fly" approach, every time the energy and its derivatives are needed for the integration of the equations of motion, they are obtained directly from quantum chemical calculations. This approach started to become practical in the mid-1990s as a result of increased availability of inexpensive computer resources and improved computational chemistry software. The application of direct dynamics calculations has grown rapidly over the last 25 years and would require a lengthy review article. The present Account is limited to some of our contributions to methods development and various applications. To improve the efficiency of direct dynamics calculations, we developed a Hessian-based predictor-corrector algorithm for integrating classical trajectories. Hessian updating made this even more efficient. This approach was also used to improve algorithms for following the steepest descent reaction paths. For larger molecular systems, we developed an extended Lagrangian approach in which the electronic structure is propagated along with the molecular structure. Strong field chemistry is a rapidly growing area, and to improve the accuracy of molecular dynamics in intense laser fields, we included the time-varying electric field in a novel predictor-corrector trajectory integration algorithm. Since intense laser fields can excite and ionize molecules, we extended our studies to include electron dynamics. Specifically, we developed code for time-dependent configuration interaction electron dynamics to simulate strong field ionization by intense laser pulses. Our initial application of ab initio direct dynamics in 1994 was to CH2O → H2 + CO; the calculated vibrational distributions in the products were in very good agreement with experiment. In the intervening years, we have used direct dynamics to explore energy partitioning in various dissociation reactions, unimolecular dissociations yielding three fragments, reactions with branching after the transition state, nonstatistical dynamics of chemically activated molecules, dynamics of molecular fragmentation by intense infrared laser pulses, selective activation of specific dissociation channels by aligned intense infrared laser fields, angular dependence of strong field ionization, and simulation of sequential double ionization.

Evolution characteristics and simulation prediction of forest and grass landscape fragmentation based on the “Grain for Green” projects on the Loess Plateau, P.R. China

Landscape fragmentation is one of the major environmental challenges to sustainable development under the background of global climate change. Grassland and forest land are the largest landscape types, which have contributed the most to ecosystem services on the Loess Plateau. However, there is no precedent for the combined study of the landscape fragmentation of forest and grassland ecosystems. In particular, there is still a lack of clear spatial significance and a quantitative description of fragmentation at the regional scale. Based on the implementation background for the “Grain for Green” Project, we selected the Loess Plateau as the research area and used the coupled future land use simulation (FLUS) model and landscape fragmentation model to explore the temporal and spatial changes in forest and grass landscape fragmentation. The results showed that (1) Woodland, grassland, and cropland are the main landscape types, and the area of cropland initially increased and then decreased, while the area of woodland and grassland exhibited the opposite trend. In particular, the period from 2000 to 2015 was forest and grass restoration stage. (2) The kappa coefficient was 0.85, and the figure of merit coefficient (FOM) was 0.11 for a 1% random sampling when using FLUS model to predict the land use, and the simulation results are also consistent with the objective change in the current social and economic development. (3) The fragmentation of woodland and grassland were dominated by edge type and core type, and the core type had an absolute advantage. It is predicted that the landscape fragmentation will gradually slowdown in 2030 under different intensities of the “Grain for Green” project. The dynamics of landscape fragmentation are conducive to the reasonable planning and objective evaluation of woodland and grassland spatial allocation and quality improvement.

Photodissociation of water induced by a long UV pulse and probed by high-energy-resolution x-ray-absorption spectroscopy

A UV-pump x-ray-probe (UVX-PP) experiment for probing UV initiated dissociation of the water molecule with long pulses is proposed on the basis of theoretical simulations. With long overlapping UV and x-ray pulses, we can obtain high-spectral-resolution x-ray-absorption or ionization spectra, containing detailed information about dynamics in the intermediate valence-excited state. The dynamics can be influenced with frequency detuning of the pump UV pulse, which acts as a camera shutter by regulating the duration of the UVX-PP process. Thereby, this UVX-PP setup gives access to ultrafast dynamics of the nuclear wave packet without experimentally challenging requirements of ultrashort pulses and controlled delay times. In a case study of the water molecule, we focus on the lowest UVX-PP channel ($1{b}_{1}\ensuremath{\rightarrow}4{a}_{1}, 1{a}_{1}\ensuremath{\rightarrow}1{b}_{1}$) where both intermediate valence-excited and final core-excited states are dissociative. The variation of the UVX-PP duration, controlled by the UV detuning, and different dispersion laws of so-called molecular and atomic bands allow one to study the dynamics of fragmentation of the water molecule in the intermediate state. A feature is that the long lifetime of intermediate valence-excited states opens a door for studies of photoinduced dissociation of polyatomic molecules with heavy fragments.

The politics of alliances. The making and breaking of social movement coalitions. Introduction to the special issue

ABSTRACT This special issue will focus on processes and mechanisms of the making and unmaking of alliances among different grassroots, civil society, and social movement organizations. The formation of alliances is a key principle and basic mechanism of mobilization and the emergence of social movements. When focusing on why and how alliances emerge, social movement scholars tend to neglect that the making and breaking of coalitions is embedded in and interacting with broader social dynamics of societal fragmentation and convergence. We understand the politics of alliances as a process in which decisions about friends and foes are made and where increased attachment toward one’s group helps to consolidate the constituency and create a feeling of belonging, but by doing so also accentuates antagonism and conflict structures in society, crystallizing interests into opposing fractions. Such dynamics often happen at the same time. Social movements may foster ideological alignment and belonging with some actors while creating more ideological distance towards others – thereby shaping the overall structure of societal relations. The contributions in the special issue build upon existing research on alliances and expands it – focusing on different friends and foes dynamics – in three important aspects: First, they look at how alliance formation interacts with the (re-)making of social boundaries and identities. Second, they address the consequences alliance formation can have across levels and contexts. Third, they explicitly look into cases where alliances fail or dissolve, and thus address the consequences of (un)making alliances.

Fragmentation of CF4q+ (q=2,3) induced by 1-keV electron collisions

We report on an investigation on the fragmentation dynamics of $\mathrm{C}{{\mathrm{F}}_{4}}^{q+}$ $(q=2,3)$ induced by 1-keV electron collisions utilizing an ion momentum imaging spectrometer. From the time-of-flight correlation maps five dominating dissociation channels of $\mathrm{C}{{\mathrm{F}}_{4}}^{2+}$ as well as one three-body fragmentation channel of $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}$ are identified. The kinetic energy release (KER) distributions for these channels are obtained and compared with the data available in the literature. The Dalitz-like momentum diagram and the Newton diagram are employed to analyze the breakup mechanism in the three-body fragmentation channel. We found that, for $\mathrm{C}{{\mathrm{F}}_{4}}^{2+}$ dissociation into ${\mathrm{F}}^{+}+\mathrm{C}{{\mathrm{F}}_{2}}^{+}+\mathrm{F}$, ${\mathrm{F}}^{+}+\mathrm{C}{\mathrm{F}}^{+}+2\mathrm{F}$, and ${\mathrm{F}}^{+}+{\mathrm{F}}^{+}+{\mathrm{CF}}_{2}$, the concerted breakup is the dominating process. Channel ${\mathrm{C}}^{+}+{\mathrm{F}}^{+}+3\mathrm{F}$ is dominated by the initial charge separation, i.e., $\mathrm{C}{{\mathrm{F}}_{4}}^{2+}\ensuremath{\rightarrow}{\mathrm{F}}^{+}+\mathrm{C}{\mathrm{F}}^{+}+2\mathrm{F}\ensuremath{\rightarrow}{\mathrm{C}}^{+}+{\mathrm{F}}^{+}+3\mathrm{F}$. With the help of the native frame method, we assigned one sequential pathway and two concerted pathways for channel $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}\ensuremath{\rightarrow}{\mathrm{F}}^{+}+{\mathrm{F}}^{+}+\mathrm{C}{{\mathrm{F}}_{2}}^{+}$. The branching ratios of these pathways are determined. The momentum correlation of the fragments and the deduced KER distribution indicate that different excited states of $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}$ with different geometries are responsible for these three pathways. The Coulomb explosion model simulation shows that most of the events in this channel are produced by $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}$ ions that have deformed geometries from the neutral ${\mathrm{CF}}_{4}$ molecule.

Ultrafast ring-opening fragmentation dynamics of C6H63+ induced by electron-impact ionization

The fragmentation dynamics of triply charged benzene [(${\mathrm{C}}_{6}{\mathrm{H}}_{6}{)}^{3+}$] induced by 260 eV electron-impact ionization are investigated using a multiparticle coincidence momentum spectrometer. By measuring three fragment ions and one outgoing electron in quadruple coincidence, we identify the complete three-body dissociation channels of ${{\mathrm{CH}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{3}}^{+} + {\mathrm{C}}_{3}{\mathrm{H}}^{+}, {{\mathrm{CH}}_{3}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{3}{\mathrm{H}}^{+}$, and ${\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+}$. We determine the projectile-energy-loss spectra, Dalitz plots, Newton diagrams, momentum correlation maps, and kinetic-energy release for each fragmentation channel. The analysis of these spectra is supported by an ab initio molecular dynamics simulation, which provides a molecular movie of the dissociation process. Our study reveals sequential mechanisms for all three dissociation channels of (${\mathrm{C}}_{6}{\mathrm{H}}_{6}{)}^{3+}$ trication, i.e., an ultrafast ring-opening reaction followed by two subsequent Coulomb-explosion processes.

Arnold web and dynamical tunneling in a four-site Bose–Hubbard model

We present the quantum and classical study of a four-well trapped Bose–Einstein condensate (BEC) modeled by the Bose–Hubbard Hamiltonian. The model used is fashioned as a minimal bipartite system consisting of a trimer coupled weakly to a monomer. Semiclassical insights into the fragmentation dynamics of the condensate is obtained by mapping out the Arnold web of the high dimensional classical phase space. A remarkable one-to-one correspondence between the quantum state space in occupation number representation and the classical Arnold web in action space is observed. The relevance of dynamical tunneling for the dynamics of Fock states near resonance junctions on the Arnold web is highlighted. We also predict the possibility of manipulating the transport within the trimer subsystem due to the weak coupling to the monomer.

Insights into the dynamic trajectories of protein filament division revealed by numerical investigation into the mathematical model of pure fragmentation.

The dynamics by which polymeric protein filaments divide in the presence of negligible growth, for example due to the depletion of free monomeric precursors, can be described by the universal mathematical equations of 'pure fragmentation'. The rates of fragmentation reactions reflect the stability of the protein filaments towards breakage, which is of importance in biology and biomedicine for instance in governing the creation of amyloid seeds and the propagation of prions. Here, we devised from mathematical theory inversion formulae to recover the division rates and division kernel information from time-dependent experimental measurements of filament size distribution. The numerical approach to systematically analyze the behaviour of pure fragmentation trajectories was also developed. We illustrate how these formulae can be used, provide some insights on their robustness, and show how they inform the design of experiments to measure fibril fragmentation dynamics. These advances are made possible by our central theoretical result on how the length distribution profile of the solution to the pure fragmentation equation aligns with a steady distribution profile for large times.

Spectroscopy and Infrared Photofragmentation Dynamics of Mixed Ligand Ion-Molecule Complexes: Au(CO)x(N2O)y.

We report a combined experimental and computational study of the structure and fragmentation dynamics of mixed ligand gas-phase ion-molecule complexes. Specifically, we have studied the infrared spectroscopy and vibrationally induced photofragmentation dynamics of mass-selected Au(CO)x(N2O)y+ complexes. The structures can be understood on the basis of local CO and N2O chromophores in different solvation shells with CO found preferentially in the core. Rich fragmentation dynamics are observed as a function of complex composition and the vibrational mode excited. The dynamics are characterized in terms of branching ratios for different ligand loss channels in light of calculated internal energy distributions. Intramolecular vibrational redistribution appears to be rapid, and dissociation is observed into all energetically accessible channels with little or no evidence for preferential breaking of the weakest intermolecular interactions.

Modeling of penetration process of fragments in ballistic gelatin

Modeling the penetration process in soft tissue simulant is the basis for evaluating the damaging efficiency of projectiles. To investigate the penetration dynamics of fragments in gelatin, this paper presented a model describing both the penetration resistance and the temporary cavity dynamics. The modeling process was set up using the law of energy conversion and conservation. The equations for the movement of the penetrator and the movement of the target medium are closely combined through sharing the same set of parameters. Penetration experiments were conducted using fragments of two different shapes: cylinder and rhombus. By comparing with the experimental results, the parameters in the present model were estimated and discussed thoroughly. The present model can predict the movement of the penetrator and the cavity expansion in the target with satisfactory accuracy.

Three-body fragmentation mechanism of C2H43+ produced by 18−keV/uNe8+ impact

In this article we present the three-body fragmentation dynamics of ${\mathrm{C}}_{2}{{\mathrm{H}}_{4}}^{3+}$ caused by $18\text{\ensuremath{-}}\mathrm{keV}/\mathrm{u}\phantom{\rule{0.16em}{0ex}}{\mathrm{Ne}}^{8+}$ ion impact. Utilizing the cold target recoil ion momentum spectroscopy, the complete kinematical information of three fragmentation channels, i.e., ${\mathrm{C}}_{2}{{\mathrm{H}}_{4}}^{3+}\ensuremath{\rightarrow}{\mathrm{H}}^{+}+{\mathrm{H}}^{+}+{\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+}, {\mathrm{H}}^{+}+\mathrm{C}{\mathrm{H}}^{+}+\mathrm{C}{{\mathrm{H}}_{2}}^{+}$, and ${\mathrm{H}}^{+}+{{\mathrm{H}}_{2}}^{+}+{\mathrm{C}}_{2}{\mathrm{H}}^{+}$ is obtained. For each channel, both concerted and sequential fragmentation mechanisms are observed and differentiated through the momentum correlation of resultant fragments visualized by the Dalitz plot and the Newton diagram. In particular, for the channel ${\mathrm{C}}_{2}{{\mathrm{H}}_{4}}^{3+}\ensuremath{\rightarrow}{\mathrm{H}}^{+}+{\mathrm{H}}^{+}+{\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+}$, it is found in addition to the sequential pathway that the two protons can be emitted concertedly in two ways, i.e., from the same carbon atom or from the two carbon atoms. The present results show a more diverse molecular fragmentation triggered by ion collisions in contrast to a previous study using intense laser field ionization.