A new ion desorption method is described that utilizes a primary beam of massive, multiply charged cluster ions to generate secondary ions of peptides in a glycerol matrix. The massive cluster ion beam is generated via electrohydrodynamic emission using a 1.5 M solution of ammonium acetate in 30% aqueous glycerol. Negative ion spectra of peptides obtained using this technique show greatly decreased relative intensities for fragment ions and 'chemical noise' background when compared to spectra obtained using a xenon atom primary beam. The near absence of fragments derived from radiation damage to the sample solution is attributed to the impact of primary particles with energies less than 1 eV/nucleon.
A relativistic Kohn-Sham density functional procedure by means of direct perturbation theory. II. Application to the molecular structure and bond dissociation energies of transition metal carbonyls and related complexes Dissociation energies for carbon cluster ions (C+ 2-15): A system where photodissociation is misleading J. Chem. Phys. 95, 4719 (1991); 10.1063/1.461743Collision induced dissociation of metal cluster ions: Bare aluminum clusters, Al+ n (n=3-26)The reactions of mass selected aluminum cluster ions, Al+ n (n=4-25), with oxygen Collision-induced dissociation (CIO) of cooled, mass selected aluminum cluster ions (AI + ) 2-7 by xenon, has been studied over an energy range of 0-1 0 e V (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 All to 2.25 ± 0.70 eV for All. The results provide a stringent test for recent calculations on A1 2 _ 6 .
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.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.