Articles you may be interested inHighly stable and symmetric boron caged B @ Co 12 @ B 80 core-shell cluster Appl. Phys. Lett. 94, 133102 (2009); 10.1063/1.3111444 Formation of hydrogenated boron clusters in an external quadrupole static attraction ion trap A combined experimental and theoretical study of the reactivity of small boron cluster cations with HF is reported on in this article. Cross sections for the reaction of mass-selected boron ͑B n ϩ , n ϭ2 -14͒ and boron monohydride ͑B n H ϩ , nϭ4, 7, and 10͒ cluster ions with HF are reported for collision energies from 0.1 to 10 eV. The reaction proceeds via a chemically bound intermediate complex, and the major product channels involve elimination of BF or H from the B n HF ϩ intermediate. Both reactivity and product branching depend strongly on cluster size. Reactivity at low energies generally decreases with increasing size, with the appearance of significant bottlenecks to reaction. The effect of adding a hydrogen atom to the reactant clusters was examined for several cluster sizes. In contrast to the boron oxides, hydrogenation of elemental boron cluster ions has little effect on reactivity with HF, suggesting that H does not compete effectively for HF binding sites. The results provide a sensitive test for the accuracy of ab initio calculations on B n ϩ and B n H ϩ and B n F ϩ , and the calculations provide insight into the reaction mechanism and effects of cluster structure on reactivity.

We have studied reactions of thermalized, mass-selected boron oxide (B,?O,,,+, n = 1-3, m = 1-4) and hydrogenated boron oxide (HB,,O,,,+, n = 1, 2, m = 1-3) ions with HF. Cross sections are reported for each product channel for collision energies ranging from 0.1 to 10 eV (center of mass). On the basis of the observed collision energy dependence, product branching, and effects of hydrogenation, we propose a reaction mechanism where facile reaction occurs only at certain sites on the oxide, most likely at terminal -B=O groups. H atom addition greatly decreases reactivity, apparently by blocking the reactive sites. Our data also point out several significant uncertainties in the literature thermochemistry for B/O/F/H species, and we are able to give some limits on AHi for several molecules.

We have found focusing/operating conditions that allow use of a commercial quadrupole mass filter for producing ion beams that simultaneously have high mass and kinetic energy resolution, and good transmission efficiency. Under proper conditions, our design perturbs the ion beam energy distribution by only ∼50 meV, while allowing mass resolution (M/ΔM)≥100, and net transmission of ∼50%. The critical factors are injection/collection lens design, an exit aperture which rejects ions that have been strongly perturbed, and stable dc balance in the quadrupole electronics.

Reactions of B n O m + and B n O m H+ clusters (n ≤ 3, m ≤ 4) with D2O have been studied over a collision energy range from 0.1 to 10 eV (center of mass). The reactivity and product branching are found to be highly dependent on the structure of the reactant ion. When available, the preferred site of attack is on a terminal B atom, and the chemistry is dominated by O and OD addition. Even for the most reactive clusters the peak reaction efficiency is only 5−7%, indicating the presence of a bottleneck to reaction. When the reactant has no terminal B atoms, reaction is 1 order of magnitude less efficient and appears to be dominated by attack at nonterminal B atoms. The B n O m H+ react similarly, suggesting that the added H atom does not block the reactive sites. This is in contrast to the isoelectronic reaction with HF, where H addition decreased reactivity dramatically. The results are compared with those for related reactions, and with recent ab initio results. In general, theory is consistent with experiment; however, there remain a few problem species.

Articles you may be interested inAb initio study of electron-ion structure factors in binary liquids with different types of chemical bonding