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Reaction pathways and rate constants of gas-phase uranium and uranium oxide ions with O 2 and H 2 O have been investigated using a quadrupole ion trap mass spectrometer (QIT-MS). A new reaction pathway is identified for the reaction between U 2+ and H 2 O, which leads to the formation of UO + via the intermediate UOH 2+ . Reaction rate constants are determined for several reactions by measuring the reaction rate at different partial pressures of the reagent gas and are found to be in reasonable agreement with the literature. These rate constants include the first known measurement for the reaction of U 2+ with H 2 O (∼0.4 k ADO ). New limits on thermochemical values are also provided for certain species. These include ∆H f (UO 2+ ) e 1742 kJ mol -1 and 1614 e ∆H f (UOH 2+ ) e 1818 kJ mol -1 and are based on the assumption that only exothermic or thermoneutral reactions are possible under the conditions used. This assumption is supported by simulations of the root-mean-square (RMS) ion kinetic energy of stored uranium ions in the QIT. Only a slight increase in the RMS ion kinetic energies, from 0.1 to 0.2 eV, is predicted over the range of trapping conditions studied (0.05 e q z e 0.75) corresponding to a theoretical reaction temperature of ∼384 K. The simulations also compare helium and neon as bath gases and show that the RMS kinetic energies are found to be very similar at long trapping times (>20 ms), although neon establishes steady state conditions in approximately half the time.

Evidence is provided that illustrates quadrupole ion traps can be used to selectively attenuate strongly bound diatomic ions occurring at the same nominal mass as an analyte ion of interest. Dissociation rates for TaO 1 (D 0 y 750 kJ mol 21 ) are found to be at least an order of magnitude larger than the loss rate of Au 1 due to scattering under ''slow heating'' resonance excitation conditions at q z ~0.67 and using neon as the bath gas. This rate difference is sufficient for the selective removal of this strongly-bound diatomic ion over the loss of the Au 1 at the same mass-to-charge ratio. Other examples of quadrupole ion trap CID for the selective reduction of common plasma-generated species are also evaluated by examining the dissociation of GdO 1 in the presence of Yb 1 , and Cu 2 1 in the presence of Te 1 . In each case, a different method of applying the excitation signals is presented, and the attenuation rates for the diatomic species due to CID are substantially larger than scattering losses for the bare metal ions. Evidence is also presented that demonstrates CID can be accomplished in concert with a slow mass analysis scan, thereby providing a means of (1) eliminating polyatomic ions (formed in the plasma or reaction cell) over an extended mass range, (2) recovering metal ion signal from the metal-containing polyatomic ions, and (3) minimizing deleterious secondary reactions of product ions.

Ti) to use for discrimination among the glass samples. This multi-element discrimination showed a significant improvement in the discrimination statistics over using only refractive index (RI) measurements. Oak Ridge National Laboratory (ORNL) recently analyzed fragments from 76 of the original side window fragments using inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS analyses measured 45 elements using a hierarchical sampling scheme to estimate variances due to sampled population (V P ), variance due to sample dissolution and within sample heterogeneity (V D ), and variance due to replicate measurements (V M ). The between-to-within ratio [B/W ~VP /(V D 1 V M )] afforded a measure of the variance within the population to that in the analytical measurement, providing a first approximation of the discriminating power of each element. Florida International University updated the RI measurements on 72 available glass fragments. These RI measurements along with ICP-AES and ICP-MS elemental analyses were used for pairwise comparisons of all possible pairs of the 72 glasses that had a complete set of measurements. The pairwise comparisons used Tukey's HSD method to compare RI and element-by-element discrimination potential of ICP-AES and ICP-MS for analyzing glass in forensic casework.