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We report on collisions of multiply charged ions with free Bi nanoparticles in the gas phase. The nanoparticles contain up to 650 Bi atoms corresponding to a diameter of 3.5 nm. The stability limit of multiply charged Bi clusters has been investigated yielding appearance sizes for Bi clusters in charge states up to $q=6$, which are in good agreement with predictions of the liquid drop model. This finding underlines the metallic character of the Bi particles. By coincidence measurements the correlation between the dominant fragments ${\mathrm{Bi}}^{+}$ and ${{\mathrm{Bi}}_{3}}^{+}$ and larger multiply charged residues has been determined. The comparison of the kinetic energies with $Q$-value calculations within the liquid drop model allowed identifying specific decay processes as two-body asymmetric fission or multifragmentation events. The higher kinetic energies of singly charged monomer ions compared to that of trimer ions are explained by a higher fissility of the decaying system. Correlation islands for small fragments indicate different decay mechanisms based on two-step processes where a third undetected fragment can be emitted in the first or the second step.

International audience; We have studied collisions between 22.5 keV He2+ ions and mixed clusters [(C60)m(C24H12)n] of m C60 and n coronene molecules where m and n range up to about ten. Surprisingly, the cluster fragmentation behavior in distant collisions is dramatically different for pure coronene clusters (m=0) and clusters containing a single C60 molecule (m=1). In the latter case, the clusters may be ionized without also being fragmented on the experimental time scale of tens of microseconds. This does not occur for pure coronene clusters, but is a main characteristic of pure fullerene clusters. For ion trajectories penetrating the mixed cluster, we observe covalent bond formations between C59 or C58 and C60, but not between coronene fragments and C60, or between C60 fragments and coronene. These results are explained by means of classical molecular dynamics simulations of collisions inside the fragmenting mixed clusters.

Dumbbell-shaped fullerene dimers C-118(+) and C-119(+) have recently been observed in mass spectra resulting from collisions between clusters of C-60 molecules and keV He2+ or Ar2+ ions [H. Zettergren et al., Phys. Rev. Lett. 110, 185501 (2013) and F. Seitz et al., J. Chem. Phys. 139, 034309 (2013)]. To unveil the formation mechanisms of these fullerene dimers, systematic molecular dynamics (MD) simulations based on the self-consistent charge density functional tight-binding method have been performed for C-n(+) + C-60 (n = 58,59,60) collisions following prompt atom knockouts by the fast ions. The statistics from the MD simulations indicate a much higher reactivity of C-59(+) and C-58(+) fragments compared to that of C-60(+). It is found that the covalently bonded dumbbell-shaped fullerene dimers C-118(+) and C-119(+) can be formed at very low-collision energies within 1 ps and are stable enough to survive on the microsecond time scale of the experiment. The thermodynamic and kinetic stabilities, as well as the bonding features, have been investigated for the most stable dumbbell dimers C-118(+), C-119(+), and C-120(+).

We report on the absolute total electron-trimethylphosphine scattering cross section (TCS) measured from 0.4 to 400 eV using a linear electron-beam attenuation method. The experimental TCS energy function exhibits very pronounced asymmetric enhancement peaked near 5.5 eV. Calculations were also carried out to obtain the integral elastic and ionization cross sections at intermediate and high energies using the independent atom and the binary-encounter-Bethe approximations, respectively. Their sum, the computed total cross section, is for intermediate energies in a reasonable agreement with the present experimental TCS data. Furthermore, the measured TCS for P(CH{sub 3}){sub 3} is compared with the TCSs for some other phosphines [PH{sub 3}, PF{sub 3}] and other methides [B(CD{sub 3}){sub 3}, N(CH{sub 3}){sub 3}]. Analysis clearly shows that exterior atoms of a molecule influence the scattering process more significantly than the central atom.

The absolute total cross section (TCS) for electron collisions with tetrahydrofuran ${\mathrm{C}}_{4}{\mathrm{H}}_{8}\mathrm{O}$ in the gas phase has been measured using the linear transmission technique within $1\char21{}370\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ energy range. The total cross section function for ${e}^{\ensuremath{-}}\text{\ensuremath{-}}{\mathrm{C}}_{4}{\mathrm{H}}_{8}\mathrm{O}$ collisions is characterized by the relatively high magnitude and the broad enhancement spanned between 4 and $12\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, with some resonantlike structures. This enhancement can be explained as a result of overlapping core-excited resonances. At higher collision energies the magnitude of the measured total cross section monotonically decreases with the energy increase. At low impact energies some additional weak resonant features are visible near 1.9 and $3.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The reported TCS results are higher by 30% than recently published by Zecca et al. [J. Phys. B 38, 2079 (1995)]. They are also distinctly different from the recent $R$-matrix calculations. At intermediate energy range the present data agree well with the sum of calculated elastic and ionization cross sections.

Absolute total cross section (TCS) for electron scattering by boron trichloride (BCl{sub 3}) molecules has been measured in a linear transmission method under single collision conditions. Measurements have been performed within electron energy range from 0.3 to 370 eV. The TCS energy function for BCl{sub 3} is dominated with very pronounced enhancement peaked near 10 eV (61x10{sup -20} m{sup 2} in the maximum). Low-energy slope of the enhancement is superimposed with two resonantlike structures located near 3.2 and 6.0 eV. On the descending high-energy side of the TCS curve only a weak shoulder between 30 and 60 eV is discernible. The present TCS is compared with the existing experimental and calculated cross sections for particular e{sup -}-BCl{sub 3} scattering processes. Furthermore, the TCS for BCl{sub 3} is also confronted with the TCS for BF{sub 3} and the role of peripheral atoms in molecule is indicated and discussed.

Absolute total cross sections (TCS's) for 0.5-370-eV electrons scattered by nitrogen trifluoride (NF{sub 3}) molecules have been measured using a linear transmission method under single collision conditions. It was found that the TCS energy function for NF{sub 3} is dominated with two pronounced enhancements: one resonantlike centered between 2 and 3 eV with the maximum value of 28x10{sup -20} m{sup 2} followed with a minimum at around 7-12 eV({approx}17x10{sup -20} m{sup 2}), and the second much broader enhancement located around 40 eV (19x10{sup -20} m{sup 2} in the maximum). The low-energy enhancement is superimposed with some weak features located near 1.8, 2.2, and 2.8 eV. The integral elastic cross section has been calculated at intermediate energies using an independent atom method with a static plus polarization model potential. The cross section for ionization has been computed as well using the binary-encounter-Bethe approach. The sum of calculated cross sections reasonably reproduces the intermediate-energy experimental TCS, with respect to the shape and value. The TCS for NF{sub 3} is also compared with the TCS for ammonia (NH{sub 3}) which was supplementary measured and the effect of substitution of fluorine atoms for hydrogen (perfluorination effect) is demonstrated and discussed.