The reactivity pattern of small (approximately 10 to 20 atoms) anionic aluminum clusters with oxygen has posed a long-standing puzzle. Those clusters with an odd number of atoms tend to react much more slowly than their even-numbered counterparts. We used Fourier transform ion cyclotron resonance mass spectrometry to show that spin conservation straightforwardly accounts for this trend. The reaction rate of odd-numbered clusters increased appreciably when singlet oxygen was used in place of ground-state (triplet) oxygen. Conversely, monohydride clusters AlnH-, in which addition of the hydrogen atom shifts the spin state by converting formerly open-shell structures to closed-shell ones (and vice versa), exhibited an opposing trend: The odd-n hydride clusters reacted more rapidly with triplet oxygen. These findings are supported by theoretical simulations and highlight the general importance of spin selection rules in mediating cluster reactivity.

Aberrant glycosylation of human glycoproteins is related to various physiological states, including the onset of diseases such as cancer. Consequently, the search for glycans that could be markers of diseases or targets of therapeutic drugs has been intensive. Here, we describe a high-throughput ion mobility spectrometry/mass spectrometry analysis of N-linked glycans from human serum. Distributions of glycans are assigned according to their m/z values, while ion mobility distributions provide information about glycan conformational and isomeric composition. Statistical analysis of data from 22 apparently healthy control patients and 39 individuals with known diseases (20 with cirrhosis of the liver and 19 with liver cancer) shows that ion mobility distributions for individual m/z ions appear to be sufficient to distinguish patients with liver cancer or cirrhosis. Measurements of glycan conformational and isomeric distributions by IMS-MS may provide insight that is valuable for detecting and characterizing disease states.

Whereas boron has many hydrides, aluminum has been thought to exhibit relatively few. A combined anion photoelectron and density functional theory computational study of the Al4H-6 anion and its corresponding neutral, Al4H6, showed that Al4H6 can be understood in terms of the Wade-Mingos rules for electron counting, suggesting that it may be a borane analog. The data support an Al4H6 structure with a distorted tetrahedral aluminum atom framework, four terminal Al-H bonds, and two sets of counter-positioned Al-H-Al bridging bonds. The large gap between the highest occupied and the lowest unoccupied molecular orbitals found for Al4H6, together with its exceptionally high heat of combustion, further suggests that Al4H6 may be an important energetic material if it can be prepared in bulk.

The nucleoside parent anions 2(')-deoxythymidine(-), 2(')-deoxycytidine(-), 2(')-deoxyadenosine(-), uridine(-), cytidine(-), adenosine(-), and guanosine(-) were generated in a novel source, employing a combination of infrared desorption, electron photoemission, and a gas jet expansion. Once mass selected, the anion photoelectron spectrum of each of these was recorded. In the three cases in which comparisons were possible, the vertical detachment energies and likely adiabatic electron affinities extracted from these spectra agreed well with the values calculated both by Richardson et al. [J. Am. Chem. Soc. 126, 4404 (2004)] and by Li et al. [Radiat. Res. 165, 721 (2006)]. Through the combination of our experimental results and their theoretical calculations, several implications emerge. (1) With the possible exception of dG(-), the parent anions of nucleosides exist, and they are stable. (2) These nucleoside anions are valence anions, and in most cases the negative charge is closely associated with the nucleobase moiety. (3) The nucleoside parent anions we have generated and studied are the negative ions of canonical, neutral nucleosides, similar to those found in DNA.

The transport of ions through multiple drift regions is modeled in order to develop an equation that is useful for an understanding of the resolving power of an overtone mobility spectrometry (OMS) technique. It is found that resolving power is influenced by a number of experimental variables, including those that define ion mobility spectrometry (IMS) resolving power: drift field (E), drift region length (L), and buffer gas temperature (T). However, unlike IMS, the resolving power of OMS is also influenced by the number of drift regions (n), harmonic frequency value (m), and the phase number (ϕ) of the applied drift field. The OMS resolving power dependence upon the new OMS variables (n, m, and ϕ) scales differently than the square root dependence of the E, L, and T variables in IMS. The results provide insight about optimal instrumental design and operation.

The photoelectron spectrum of the uracil-H 2 S anionic complex (UH 2 S) -has been recorded with 2.540 eV photons. Unlike the (uracil-H 2 O) -spectrum, which displays a broad feature with maximum at about 0.9 eV, the (UH 2 S) -spectrum reveals a broad feature with a maximum between 1.7 and 2.1 eV. The latter vertical detachment energy value is too large to be attributed to an (UH 2 S) -complex in which an intact uracil anion is solvated by H 2 S. The effects of electron attachment to the UH 2 A complexes (A ) Se, S, O) have been studied at the density functional theory level with the B3LYP and MPW1K exchange correlation functionals as well as at the second-order Møller-Plesset perturbation theory level. The three acids cover a broad range of acidity with calculated gas-phase deprotonation enthalpies being equal to 14.8, 15.1, and 16.9 eV for H 2 Se, H 2 S, and H 2 O, respectively. In the case of H 2 Se and H 2 S, electron attachment is predicted to induce a barrier-free proton transfer (BFPT) from the acid to the O8 atom of uracil, with the product being the radical of hydrogenated uracil bound to AH -. No BFPT is predicted for the anion of uracil with H 2 O. Critical factors for the occurrence of BFPT have been analyzed, and the role of the stabilizing interaction between the hydrogenated uracil and the deprotonated acid has been discussed. Four structures have been considered for every UH 2 A complex, and their relative stabilities are different for the neutral and anionic species. The increased stabilities of anionic complexes that undergo BFPT can be related to the properties of the second hydrogen bond (C5H‚‚‚A or N1(3)H‚‚‚A). In comparison with the case of neutral structures, this bond is weakened for anionic structures without BFPT and strengthened for those with BFPT.

The growing use of explosives by terrorists and criminals creates a need for instrumentation which can rapidly analyze these energetic compounds, preferably on site. Direct analysis in real time (DART) is a promising technology for surface analysis with little or no sample preparation. Therefore, DART ionization is evaluated for use in detecting explosives on solid substrates and in liquid matrices. Fifteen explosives were chosen as a consequence of their common usage. Five surfaces were chosen to represent a wide range of physical properties such as composition, porosity, surface morphology, and thermal and electrical conductivity. Additionally these surfaces are commonly found in everyday surroundings. All 75 compound‐surface combinations produced a clear, easily identifiable, mass spectra characteristic of the targeted analyte. Simultaneous detection of five explosives is demonstrated on these same surfaces. Lastly, rapid detection of trace contamination in common fluids is also explored.

Anion photoelectron spectroscopy and density functional theory were employed to study aluminum hydride clusters, AlnHm- (4