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Cross sections for oxidation reactions of boron cluster ions (B+1–14) with CO2 are reported as a function of collision energy. The results give insight into the oxidation mechanism and are a sensitive probe of the B+n–O bond energy. In addition, collision-induced dissociation (CID) was used to measure the stabilities of boron monoxide cluster ions (BnO+) and energetic and structural information is obtained that indicates that at least, in some cases, oxidation causes structural rearrangement of the clusters. Sequential oxidation of boron cluster ions by CO2 was also studied and the results give further insight into the reaction mechanism and energetics. [ABSTRACT FROM AUTHOR]

Reactions of mass-selected, cooled, boron cluster ions (B+n, n=1–14) with water have been studied for collision energies from 0.1 to 6.0 eV. Most work was done with D2O, however isotope effects were examined for selected reactant cluster ions. For all size clusters there are exoergic product channels, which in most cases have no activation barriers. Cross sections are generally large, however there are fluctuations with cluster size in total reactivity, collision energy dependences, and in product distributions. For small cluster ions, there is a multitude of product channels. For clusters larger than B+6, the product distributions are dominated by a single channel: Bn-1D++DBO. Under multiple collision conditions, the primary products undergo a remarkable sequence of secondary ‘‘etching’’ reactions. As these occur, boron atoms are continuously replaced by hydrogen, and the intermediate products retain the composition: Bn-mH+m. This highly efficient chemistry appears to continue unchanged as the composition changes from pure boron to mostly hydrogen. Comparison of these results is made with boron cluster ion reactions with O2 and D2, as well as reactions with water of aluminum and silicon cluster ions. Some discussion is given of the thermochemistry for these reactions, and a possible problem with the thermochemical data in the BOD/DBO system is discussed. [ABSTRACT FROM AUTHOR]

Product cross sections for reaction of size-selected boron cluster ions with deuterium are reported for collision energies ranging from 0.05 to 10 eV. The major reactions are those in which one or two deuterium atoms add to the intact cluster. Other, higher energy channels involve fragmentation of the clusters, with and without addition of deuterium atoms. Cluster size dependent thresholds are observed for many reactions, and we have used these to estimate the cluster–D atom binding energy as a function of cluster size. Metastable adducts of the form BnD+2 are observed for reagent clusters as small as the tetramer. For small clusters, adducts form without activation energy, but starting at B+8 activation barriers are observed. Unimolecular decay rates of the adducts have been estimated, and the binding energy of D2 to various size cluster ions was extracted using RRKM modeling. Comparison is made with related results for boron surfaces and for aluminum cluster ions. [ABSTRACT FROM AUTHOR]

We report a study of the absolute cross sections, reaction threshold energies, and product branching ratios for interactions of aluminum cluster ions (Al+n, n=1–9) with O2 and N2O. Most of the reactions are observed to have collision energy thresholds which are attributed to activation barriers or bottlenecks. At collision energies above threshold, exoergic oxidation of the cluster ions occurs, and the resulting energy release causes extensive fragmentation to yield a variety of product ions. Comparison of threshold behavior for different product channels suggests that in addition to the dominant oxidation reactions, the clusters undergo Al abstraction, O2–Al+ exchange, and collision induced dissociation. [ABSTRACT FROM AUTHOR]

Collision-induced dissociation (CID) of cooled, mass selected aluminum cluster ions (Al+2–7) by xenon, has been studied over an energy range of 0–10 eV (center of mass). These experiments were carried out in a new apparatus which is described in detail. From the product branching ratios and cross section magnitudes we derive qualitative structural information about the cluster ions. The fragmentation thresholds are analyzed to yield dissociation energies, approximate ionization potentials, and further structural information about the cluster ions and their neutral counterparts. Cluster stabilities range from 0.85±0.40 eV for Al+4 to 2.25±0.70 eV for Al+7. The results provide a stringent test for recent calculations on Al2–6. [ABSTRACT FROM AUTHOR]

Cross sections for reaction of mass-selected boron cluster ions (B+n, n=2–24) with N2O are reported for collision energies from 0.1 to 10 eV. The major product channels are addition of a single nitrogen or oxygen atom to the intact cluster ion. For small clusters, there are no activation barriers and cross sections are large, however, as cluster size increases, bottlenecks and activation barriers reduce reactivity substantially. Significant size effects are observed in the product branching distributions. The dominant reaction mechanism at low collision energies is proposed to be complex formation, where only one bond in N2O is broken, followed by desorption of the stable leaving group (N2 or NO). Reactions with boron cluster ions larger than 16 atoms in size have been studied for the first time, and in addition, supporting evidence is given for our previous suggestion that B3 has an anomalously high ionization potential. Comparisons are made with other oxidation reactions of boron cluster ions, and with aluminum and silicon cluster ion reactions with N2O. [ABSTRACT FROM AUTHOR]