In order to model the fate and transport of particles following a nuclear explosion, there must first be an understanding of individual physical and chemical processes that affect particle formation. One interaction pertinent to fireball chemistry and resultant debris formation is that between uranium and oxygen. In this study, we use laser ablation of uranium metal in different concentrations of oxygen gas, either 16O2 or 18O2, to determine the influence of oxygen on rapidly cooling uranium. Analysis of recovered particulates using infrared absorption and Raman spectroscopies indicate that the micrometer-sized particulates are predominantly amorphous UOx (am-UOx, where 3 ≤ x ≤ 4) and UO2 after ablation in 1 atm of pure O2 and a 1% O2/Ar mixture, respectively. Energy dispersive X-ray spectroscopy (EDS) of particulates formed in pure O2 suggest an O/U ratio of ~ 3.7, consistent with the vibrational spectroscopy analysis. Both am-UOx and UO2 particulates convert to α-U3O8 when heated. Lastly, experiments performed in 18O2 environments show the formation of 18O-substituted uranium oxides; vibrational frequencies for am-U18Ox are reported for the first time. When compared to literature, this work shows that cooling timescales can affect the structural composition of uranium oxides (i.e., crystalline vs. amorphous). This indicator can be used in current models of nuclear explosions to improve our predicative capabilities of chemical speciation.
The millimeter-wave spectrum of the SiP radical (X2Πi) has been measured in the laboratory for the first time using direct-absorption methods. SiP was created by the reaction of phosphorus vapor and SiH4 in argon in an AC discharge. Fifteen rotational transitions (J + 1 ← J) were measured for SiP in the Ω = 3/2 ladder in the frequency range 151–533 GHz, and rotational, lambda doubling, and phosphorus hyperfine constants determined. Based on the laboratory measurements, SiP was detected in the circumstellar shell of IRC+10216, using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory at 1 mm and 2 mm, respectively. Eight transitions of SiP were searched: four were completely obscured by stronger features, two were uncontaminated (J = 13.5 → 12.5 and 16.5 → 15.5), and two were partially blended with other lines (J = 8.5 → 7.5 and 17.5 → 16.5). The SiP line profiles were broader than expected for IRC+10216, consistent with the hyperfine splitting. From non-LTE radiative transfer modeling, SiP was found to have a shell distribution with a radius ∼300 R *, and an abundance, relative to H2, of f ∼ 2 × 10−9. From additional modeling, abundances of 7 × 10−9 and 9 × 10−10 were determined for CP and PN, respectively, both located in shells at 550–650 R *. SiP may be formed from grain destruction, which liberates both phosphorus and silicon into the gas phase, and then is channeled into other P-bearing molecules such as PN and CP.
The pure rotational spectrum of ZnBr (X 2 Σ + ) has been recorded in the frequency range 259-310 GHz using millimeter-wave direct absorption techniques. This study is the first quantitative spectroscopic investigation of this free radical. ZnBr was synthesized in a DC discharge by the reaction of zinc vapor in argon with one of three reagents: BrCH 3 , Br 2 CH 2 , or Br 2 . Eight rotational transitions were measured for six isotopologues ( 64 Zn 79 Br, 64 Zn 81 Br, 66 Zn 79 Br, 66 Zn 81 Br, 68 Zn 79 Br, and 68 Zn 81 Br), all of which exhibited spin-rotation interactions. Furthermore, transitions originating in the v = 1 through 3 excited vibrational states were obtained for certain isotopologues. Five rotational transitions were also recorded for 67 Zn 79 Br, in which hyperfine splittings were observed arising from the 67 Zn nucleus (I = 5/2). The spectra were analyzed using a Hund's case (b βJ ) Hamiltonian, and rotational, spin-rotation, and 67 Zn magnetic hyperfine constants were determined. Equilibrium parameters were also derived for the 64 Zn 79 Br, 64 Zn 81 Br, 66 Zn 79 Br, and 66 Zn 81 Br isotopologues, including the vibrational constant, ω e = 286 cm −1 . The equilibrium bond length was derived to be r e = 2.268 48(90) Å. Analysis of the 67 Zn hyperfine parameters suggest a decrease in ionic character in ZnBr from the other known zinc halides, ZnF and ZnCl.
Incorporating isotopically labelled materials in degradation experiments could help unravel the mechanism(s) of decomposition through use of the kinetic isotope effect. Characterizing synthesized isotopologues however requires an understanding of what observable signals are affected by the isotopic substitution. As vibrational spectroscopy can distinguish between isotopologues, it is an ideal characterization technique to evaluate isotopic variants. To this end, the vibrational spectra of HNIW and its deuterated ( 2 H), 13 C, 15 N (all), 15 N (nitro), and 18 O isotopologues have been computationally predicted in the gas phase using density functional theory. These results are compared to experimentally measured FTIR/ATR and Raman spectra of both unsubstituted HNIW and 15 N-labeled HNIW in which the six nitro groups were synthetically tagged with 15 N atoms ( 15 N nitro À HNIW). The experimental isotopic frequency shift for the À NO 2 asymmetric stretching frequencies agrees with that theoretically calculated (~35.7 cm À 1 vs. 36.5 cm À 1 , respectively). Furthermore, analysis of the theoretically predicted frequency shifts for all isotopologues suggest the À NO 2 bending modes are lower in frequency than previously reported. This assignment is supported by the experimentally measured isotopic shift of ~10.1 cm À 1 for these features (consistent with the predicted shift of ~13.1 cm À 1 ). This work expands our current understanding of the vibrational modes in HNIW as well as provides a method for future work on similar systems.
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.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.