Elastic scattering of 21-MeV protons from nitrogen 14, oxygen 16, argon 40, nickel 58, and tin 116
Elastic scattering of 21 MeV protons from nitrogen 14, oxygen 16, argon 40, nickel 58, and tin 116
Baron, N.↗
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Detection of the Molecular Oxygen Isotopomer ^(16)O^(18)O in Interstellar Clouds
We report the first detection of molecular oxygen in interstellar clouds by observation.
Line: Identification - ISM; abundances - ISM; indi↗
Effect of the two-particle spin-orbit nucleon-nucleon interaction on the O16 and N16 nuclei Interim technical report
Two-particle spin-orbit nucleon-nucleon interaction of oxygen 16 and nitrogen 16 nuclei
NITROGEN 16↗
Semi-volatile and highly oxygenated gaseous and particulate organic compounds observed above a boreal forest canopy
Abstract. We present hourly online observations of molecular compositions (CxHyOzN0−1) and abundances of oxygenated organic species in gas and submicron particle phases from April to June of 2014 as part of the Biogenic Aerosols-Effects on Cloud and Climate (BAECC) campaign. Measurements were made using the Filter Inlet for Gases and AEROsols coupled to a high-resolution time-of-flight iodide-adduct ionization mass spectrometer (FIGAERO-CIMS) located atop a 35 m tall tower, about 10 m above a boreal forest canopy at the SMEAR II research station in Hyytiälä, Finland. Semi-volatile and highly oxygenated multifunctional (HOM) organic species possessing from 1 up to 20 carbon atoms, and with as few as 2 and as many as 16 oxygen atoms, were routinely observed. Utilizing non-negative matrix factorization, we determined that > 90 and > 99 % of the organic mass in the gas and particle phases, respectively, exhibited one of three distinct diel trends: one in which abundances were enhanced at daytime, another in the early morning hours, and thirdly during nighttime. Particulate organic nitrates contributed ∼ 35 % to the total organic aerosol mass loading at night during BAECC, much higher than observed by the same instrument package at a mixed-deciduous forest site in the southeastern US that experienced higher nighttime concentrations of nitrogen oxides. Unique HOM monomers (defined here as those with 10 carbon and 7 or more oxygen atoms) and dimers (at least 16 carbon atoms), with and without a nitrogen atom, were found in most of the three subgroups of both phases. We show the potential to connect these groupings of compounds based on their distinct behavior in time to the expected chemical conditions (biogenic VOC precursor, oxidant type, etc.) responsible for their production. A suite of nitrated dimer-like compounds was detected in both the gas and particle phases, suggesting a potential role for the formation of low-volatility organics from NO3-radical-driven, as well as daytime NO-influenced, monoterpene chemistry.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Gaseous By-Product of Thermal Vacuum Processing of Lunar Highland Simulant
Scientists at Kennedy Space Center are advancing technologies to achieve oxygen extraction on the Lunar surface. One such technology is Molten Regolith Electrolysis (MRE) in which regolith simulant is melted under high temperatures to perform oxygen extraction through electrolysis of the melt pool. A study was conducted to understand the molten formation and proper-ties of Lunar Highlands Simulants (LHS-1) under high vacuum environments ranging between 10-6 Torr. These studies include investigating the regolith melt behavior and by-product gas analysis systems to prepare for pilot plant development and operations. The off-gassing rates and pressure build-up, gaseous compounds, and material compatibility may be a risk to MRE systems. The KSC findings are reported here for inclusion into future mis-sion architecture and operational planning. The four stages of the experiment were vacuum, resistive heating, regolith melt and gas detection. The regolith mass of 70 g was melted in a 40 cm tall x 50 cm diameter vacuum chamber at temperature increase rate 47 ℃ /min and ramp rate of 1 ampere/3 min up to an 18-amp maximum. The test is conducted for about 60 minutes and the constituent gases produced during heating of regolith is monitored with a re-sidual gas analyzer. During the molten formation, primary off-gassing volatiles included water vapor (18 amu), a peak at 44 amu (FeO2 – expected), and atomic oxygen (16 amu), among a series of other compounds that could create compatibility issues such as magnesium, chlorine, and silicon oxide. These results add to the knowledge required for successful oxygen extraction on the moon.
Molten Regolith Electrolysis↗
Emergence of 4 H $J^π$ = 1 - resonance in contact theories
We obtain the s- and p-wave low-energy scattering parameters for n 3 H elastic scattering and the position of the 4 H J π = 1 - resonance using the pionless effective field theory at leading order. Results are extracted with three numerical techniques: confining the system in a harmonic oscillator trap, solving the Faddeev-Yakubovsky equations in configuration space, and using an effective two-body cluster approach. The renormalization of the theory for the relevant amplitudes is assessed in a cutoff-regulator range between 1 fm -1 and 10 fm -1 . Most remarkably, we find a cutoff-stable/RG-invariant resonance in the 4 H J π = 1 - system. This p-wave resonance is a universal consequence of a shallow two-body state and the introduction of a three-body s-wave scale set by the triton binding energy. The stabilization of a resonant state in a few-fermion system through pure contact interactions has a significant consequence for the powercounting of the pionless theory. Specifically, it suggests the appearance of similar resonant states also in larger nuclei, like 16-oxygen, in which the theory’s leading order does not predict stable states. Those resonances would provide a starting state to be moved to the correct physical position by the perturbative insertion of sub-leading orders, possibly resolving the discrepancy between data and contact EFT.
79 ASTRONOMY AND ASTROPHYSICS↗
RARE ISOTOPIC SPECIES OF SULFUR MONOXIDE: THE ROTATIONAL SPECTRUM IN THE THz REGION
Many sulfur-bearing species have been detected in different astronomical environments and have allowed us to derive important information about the chemical and physical composition of interstellar regions. In particular, these species have also been shown to trace and probe hot-core environment time evolution. Among the most prominent sulfur-bearing molecules is SO, the sulfur monoxide radical, one of the more ubiquitous and abundant, which is also observed in its isotopic substituted species such as {sup 34}SO and S{sup 18}O. Due to the importance of this simple diatomic system, and in order to face the challenge of modern radioastronomical facilities, an extension to the THz range of the rare isotopologues of sulfur monoxide has been performed. High-resolution rotational molecular spectroscopy has been employed to extend the available data set of four isotopic species, SO, {sup 34}SO, S{sup 17}O, and S{sup 18}O, up to the 1.5 THz region. The frequency coverage and spectral resolution of our measurements allowed a better constraint of the molecular constants of the four species considered, specifically focusing on the two oxygen-substituted isotopologues. Our measurements were also employed in an isotopically invariant fit including all of the available pure rotational and ro-vibrational transitions for all of the SO isotopologues, thus enabling accurate predictions of the rotational transitions at higher frequencies. We also provide comparisons with recent works performed on the same system, demonstrating the quality of our experiment and the improvement of the data sets for all of the species considered. Transition frequencies for this system can now be used with confidence by the astronomical community well into the THz spectral region.
79 ASTRONOMY AND ASTROPHYSICS↗
SU-F-J-202: Secondary Radiation Measurements for Charged Particle Therapy Monitoring: Fragmentation of Therapeutic He, C and O Ion Beams Impinging On a PMMA Target
Purpose: In Charged Particle Therapy (CPT), besides protons, there has been recently a growing interest in 4He, 12C and 16O beams. The secondary radiation produced in the interaction of those beams with a patient could be potentially used for on-line monitoring of range uncertainties in order to fully exploit the advantages of those light ions resulting from increased Radio Biological Effectiveness, reduced multiple scattering and Oxygen Enhancement Ratio. The study and precise characterization of secondary radiation (beta+, prompt gamma, charged fragments) is the cornerstone of any R&D activity aiming for online monitoring development and purpose of the analysis presented here. Methods: We present the measurements of the secondary radiation generated by He, C and O beams impinging on a beam stopping PMMA target. The data has been collected at the Heidelberg Ionbeam Therapy center (HIT), where several millions of collisions were recorded at different energies, relevant for therapeutical applications. Results: The experimental setup, as well as the analysis strategies will be reviewed. The detected particle fluxes as a function of the primary beam energy and the emission angle with respect to the beam direction will be presented and compared to the results of other available measurements. In addition, the energy spectra and emission shapes of charged secondary particles will be shown and discussed in the context of the primary beam range monitoring technique that is being developed by the ARPG collaboration, within the INSIDE project funded by the Italian research ministry. The implications for dose monitoring applications will be discussed, in the context of the current (or planned) state-of- the-art detector solutions. Conclusion: The characterization of the radiation produced by 12C, 4He and 16O beams fully supports the feasibility of on-line range monitoring in the clinical practice of CPT by means of secondary particles detection.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
O18/O16 ratios of Apollo 11 lunar rocks and minerals
Apollo 11 lunar rocks and minerals oxygen 18- oxygen 16 ratios
Epstein, S.↗
Measurement of the O-18 to O-16 isotope ratio for characterizing oxide surface layers on LDEF samples
The ratio of the density of the oxygen 18 isotope (O-18) to the density of the oxygen 16 isotope (O-16) is a strong function of altitude in the atmosphere because of the stronger gravitational attraction on the heavier isotope. It is proposed that the measurement of this ratio for oxide surface layers on LDEF samples can easily distinguish oxides formed in orbit from contaminative oxides formed during retrieval procedures. Since the satellite altitude is known as a function of time, it may be possible to use the measured ratio to determine the time of formation of oxide layers, the accuracy depending upon the stability of the atmosphere.
Sagalyn, Paul L.↗
Glass microsphere lubrication
The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the manufacturing of the microspheres, while sorting entails deciphering the good microspheres from the bad ones. Each process is discussed in detail.
Geiger, Michelle↗
Fire-related medical science
Spacecraft fire safety may be improved by the use of a fire-retardant atmosphere in occupied spaces. Low concentrations of oxygen can protect humans from fire damage by reducing the rate and spread of combustion, but care must be taken to avoid the hypoxic effects of oxygen-lean atmospheres. Crews can live and work in 11 percent oxygen if barometric pressure were adjusted to maintain the partial pressure of oxygen above 16 kPa. Eleven percent oxygen should prevent most types of fires, since 15 percent oxygen retards the combustion of paper and 13 percent oxygen extinguishes pentane flames. Test results indicate that seated humans can perform mental tasks in atmospheres containing 11.5 percent oxygen. Although this strategy of fire safety is under consideration for submarines, it could be adapted to spacecraft once operational procedures define a maximum hyperbaric pressure and fire research defines the effects of reduced oxygen concentrations on combustion in low gravity environments.
Knight, Douglas R.↗
Isobar analog states (IAS), double isobar analog states (DIAS), configuration states (CS), and double configuration states (DCS) in halo nuclei. Halo isomers
It has been shown that IAS, DIAS, CS, and DCS can simultaneously have n-n, n-p, and p-p halo components in their wave functions. Differences in halo structure of the excited and ground states can result in the formation of isomers (halo-isomers). Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei. The structure of the ground and excited states with different isospin quantum number in halo like nuclei is discussed. B(Mλ) and B(Eλ) for γ-transitions in {sup 6,7,8}Li, {sup 8,9,10}Be, {sup 8,10,11}B, {sup 10,11,12,13,14}C, {sup 13,14,15,16,17}N, {sup 15,16,17,19}O, and {sup 17}F are analyzed. Special attention is given to nuclei whose ground state does not exhibit halo structure but the excited state may have one.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
The 16-39 micron spectroscopy of oxygen-rich stars
Airborne observations of the 16-39 microns spectra of ten oxygen-rich stars with excess emission in the infrared was obtained. The stars show excess emission attributed to circumstellar dust grains in the 16-39 microns region in the form of a broad hump peaking near 18 microns and falling smoothly to longer wavelengths. The emission is similar in character to the emission from the Trapezium region of the Orion nebula indicating the grain materials are quite similar in these objects. The existence of a feature in the 20 microns region is consistent with the 0-Si-0 bending resonance expected for silicate material. The lack of any sharp structure in the spectra indicates the silicate is in an amorphous, disordered form. A simple model of small grains of carbonaceous chondrite silicate material in a diffuse circumstellar envelope is shown to give a good qualitative fit to the observed 8-39 microns circumstellar spectra. Comparison of the observed spectra with the model spectra indicates the grain emissivity falls as 1/lambda squared from 20 microns to 40 microns.
Forrest, W. J.↗
16-39 micron spectroscopy of oxygen-rich stars
Airborne observations of the 16-39-micron spectra of 10 oxygen-rich stars with excess emission in the infrared have been obtained. The stars show excess emission attributed to circumstellar dust grains in the 16-39-micron region in the form of a broad hump peaking near 18 microns and falling smoothly to longer wavelengths. The emission is similar in character to the emission from the Trapezium region of the Orion Nebula, indicating the grain materials are quite similar in these objects. The existence of a feature in the 20-micron region is consistent with the O-Si-O bending resonance expected for silicate material. The lack of any sharp structure in the spectra indicates the silicate is in an amorphous, disordered form. A simple model of small grains of carbonaceous chondrite silicate material in a diffuse circumstellar envelope is shown to give a good qualitative fit to the observed 8-39-micron circumstellar spectra. Comparison of the observed spectra with the model spectra indicates the grain emissivity falls as the inverse square of wavelength from 20 to 40 microns.
Forrest, W. J.↗
Re-evaluation of the {sup 16}O(N, γ){sup 17}O cross section at astrophysical energies and its role as a neutron poison in the s-process
The doubly magic nucleus {sup 16}O has a small neutron-capture cross section of just a few tens of microbarns in the astrophysical energy region. Despite this, {sup 16}O plays an important role as a neutron poison in the astrophysical slow neutron capture (s) process due to its high abundance. We present in this paper a re-evaluation of the available experimental data for {sup 16}O(n,γ){sup 17}O and derive a new recommendation for the Maxwellian-averaged cross sections between kT = 5 and 100 keV. Our new recommendations are lower up to kT = 60 keV compared to the previously recommended values but up to 14% higher at kT = 100 keV. We explore the impact of this different energy dependence on the weak s-process during core helium burning (kT = 26 keV) and shell carbon burning (kT = 90 keV) in massive stars where {sup 16}O is the most abundant isotope.
79 ASTRONOMY AND ASTROPHYSICS↗
Determination of the oxide scale growth mechanism using 18O-tracer experiments in combination with Transmission Electron Microscopy and nanoscale Secondary Ion Mass Spectrometry
Highlights: • {sup 18}O-tracer experiments to determine oxide scale growth mechanism on a Fe-Cr alloy. • Cr{sub 2}O{sub 3} scale growth primarily by means of metal outwards diffusion in air at 850 °C • nanoSIMS mapping on TEM lamella more accurate than SIMS sputter depth profiling • nanoSIMS mapping on TEM lamella reveal information about local oxide growth. • Strong local variation of oxide scale growth - Abstract: Two-stage {sup 18}O{sub 2}/{sup 16}O{sub 2} exposures can be used to investigate the effect that alloying elements, secondary phases, or surface treatments have on the high temperature oxidation behaviour of certain materials. During subsequent exposures to {sup 16}O{sub 2}- and {sup 18}O{sub 2}-rich atmospheres, {sup 16}O- and {sup 18}O-rich layers are formed. Analysis of the layers using Secondary Ion Mass Spectrometry (SIMS) depth profiling allows for conclusions to be drawn about the oxide scale growth mechanism. The conclusions are, however, not entirely unambiguous due to the limited lateral resolution of the technology. Rough surface topography and the thickness variation of the oxide scale over the analysed volume add to the ambiguity of the findings. In this study, an Fe-20%Cr alloy was exposed to both {sup 18}O- and {sup 16}O-rich environments at 850 °C. Two methods were used to analyse the thermally grown Cr{sub 2}O{sub 3} scale: (1) traditional SIMS depth profiling and (2) preparation of a cross-sectional lamellae for Transmission Electron Microscopy (TEM), which, subsequently, was analysed in a NanoSIMS. The NanoSIMS {sup 16}O and {sup 18}O elemental maps were then superimposed on the TEM image. In comparison with traditional SIMS depth profiling, the nanoSIMS elemental maps reveal detailed information about local oxide growth in different parts of an oxide scale. Moreover, a clear {sup 16}O/{sup 18}O interface can be seen in the nanoSIMS maps, which is not the case in the sputter depth profiles. The findings of this study show that the aforementioned issues associated with sputter depth profiling can be eliminated by mapping a cross-section of an oxide scale using high resolution nanoSIMS.
36 MATERIALS SCIENCE↗
Differential cross section for the {sup 16}O(t, p){sup 18}O reaction and determination of the size of the two-neutron periphery in the {sup 18}O nucleus
Within the theoretical formalism that combines a four-body problem with themultiparticle shell model, it is shown that the cross section for the dineuteron-stripping mechanism is consistent with the experimental angular distribution of protons from the {sup 16}O(t, p){sup 18}O reaction. This makes it possible to find the wave function for the relative motion of the dineutron and {sup 16}O and to obtain thereby the probability density W(r) for the dineutron in {sup 18}O, the nn–{sup 16}O interaction potential, and the root-mean-square distance 〈L〉{sub nn} between the dineutron and {sup 16}O. The respective calculations reveal that, at r ≈ 8 fm, the dineutron probability density and a rather deep nn–{sup 16}O potential become negligible, which leads to the absence of a dineuntron periphery in {sup 18}O. It seems that one can explain this fact by a rather large value (12.19 MeV) of the dineutron binding energy in this nucleus. Thus, the {sup 18}O nucleus is quite compact an object, despite the excess of two neutrons, and has a neutron skin rather than a periphery.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗