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1. 40 Ar proposed as probe of neutron-induced reactions in a high-density stellar-like plasma at the National Ignition Facility

   https://doi.org/10.1051/epjconf/202327913004  

   Paul, M. ; Sahoo, R. N. ; Tessler, M. ; Jeet, J. ; Velsko, C. ; Zylstra, A. ; Avila, M. ; Dickerson, C. ; Fougères, C. ; Jayatissa, H. ; et al ( January 2023 , EPJ Web of Conferences)

   Freeman, S. ; Lederer-Woods, C. ; Manna, A. ; Mengoni, A. (Ed.)

   The thermodynamical conditions and the neutron density produced in a laser-induced implosion of a deuterium-tritium (DT) filled capsule at the National Ignition Facility (NIF) are the closest laboratory analog of stellar conditions. We plan to investigate neutron-induced reactions on 40 Ar, namely the 40 Ar( n , 2 n ) 39 Ar( t 1/2 =268 y), the 40 Ar( n , γ) 41 Ar(110 min) and the potential rapid two-neutron capture reaction 40 Ar(2 n , γ) 42 Ar(33 y) in an Ar-loaded DT capsule. The chemical inertness of noble gas Ar enables reliable collection of the reaction products. 

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2. The impact of (n,γ) reaction rate uncertainties on the predicted abundances of i-process elements with 32 ≤ Z ≤ 48 in the metal-poor star HD94028

   https://doi.org/10.1093/mnras/stz3322  

   McKay, John E. ; Denissenkov, Pavel A. ; Herwig, Falk ; Perdikakis, Georgios ; Schatz, Hendrik ( December 2019 , Monthly Notices of the Royal Astronomical Society)

   Several anomalous elemental abundance ratios have been observed in the metal-poor star HD94028. We assume that its high [As/Ge] ratio is a product of a weak intermediate (i) neutron-capture process. Given that observational errors are usually smaller than predicted nuclear physics uncertainties, we have first set-up a benchmark one-zone i-process nucleosynthesis simulation results of which provide the best fit to the observed abundances. We have then performed Monte Carlo simulations in which 113 relevant (n,γ) reaction rates of unstable species were randomly varied within Hauser–Feshbach model uncertainty ranges for each reaction to estimate the impact on the predicted stellar abundances. One of the interesting results of these simulations is a double-peaked distribution of the As abundance, which is caused by the variation of the 75Ga (n,γ) cross-section. This variation strongly anticorrelates with the predicted As abundance, confirming the necessity for improved theoretical or experimental bounds on this cross-section. The 66Ni (n,γ) reaction is found to behave as a major bottleneck for the i-process nucleosynthesis. Our analysis finds the Pearson product–moment correlation coefficient rP > 0.2 for all of the i-process elements with 32 ≤ Z ≤ 42, with significant changes in their predicted abundances showing up when the rate of this reaction is reduced to its theoretically constrained lower bound. Our results are applicable to any other stellar nucleosynthesis site with the similar i-process conditions, such as Sakurai’s object (V4334 Sagittarii) or rapidly accreting white dwarfs.

    

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3. Leaf NPK stoichiometry, δ15N , and apparent nutrient limitation of co‐occurring carnivorous and noncarnivorous plants

   https://doi.org/10.1002/ecy.3825  

   Givnish, Thomas J. ; Shiba, Zackary W. ( October 2022 , Ecology)

   Previous meta‐analyses suggested that carnivorous plants—despite access to N, P, and K from prey—have significantly lower leaf concentrations of these nutrients than noncarnivores. Those studies, however, largely compared carnivores in nutrient‐poor habitats with noncarnivores in more nutrient‐rich sites, so that the differences reported might reflect habitat differences as much as differences in nutrient‐capture strategy. Here we examine three carnivorous and 12 noncarnivorous plants in the same nutrient‐poor bog to compare their foliar nutrient concentrations, assess their patterns of nutrient limitation using leaf NPK stoichiometry, and estimate percentage N derived from prey by carnivores using a mixing model for stable N isotopes. We hypothesized that (1) carnivore leaf nutrient concentrations approach or exceed those of noncarnivores in the same nutrient‐poor habitat; (2) species in different functional groups show different patterns of stoichiometry and apparent nutrient limitation; and (3) noncarnivores might show evidence of using other means of nutrient acquisition or conservation to reduce nutrient limitation. At Fallison Bog in northern Wisconsin, carnivorous plants (Drosera rotundifolia,Sarracenia purpurea,Utricularia macrorhiza) showed significantly lower leaf percentage C and N:P ratio, higher δ¹⁵N, and no difference from noncarnivores in leaf N, P, K, and δ¹³C. Sedges had significantly lower leaf percentage P, percentage C, and N:K ratio, and higher K:P ratio than nonsedges restricted to theSphagnummat, and may tap peat N via aerenchyma‐facilitated peat oxidation (oxipeditrophy). Evergreen ericaceous shrubs exhibited significantly higher levels of percentage C and lower values of δ¹⁵N than mat nonericads.Calla palustris—growing in the nutrient‐rich moat at the bog's upland edge—had very high values of leaf N, K, δ¹⁵N, and N:P ratio, suggesting that it may obtain nutrients from minerotrophic flows from the adjacent uplands and/or rapidly decaying peat. Stoichiometric analyses indicated that most species are N limited. A mixing model applied to δ¹⁵N values for carnivores, noncarnivores, and insects produced an estimate of 50% of leaf N derived from prey forUtricularia, 42% forSarracenia, and 41% forDrosera.

    

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4. Comparing Pr 3+ and Nd 3+ for deactivating the Er 3+ :  4 I 13/2 level in lanthanum titanate glass

   https://doi.org/10.1364/OME.517790  

   Topper, Brian ; Neumann, Alexander ; Wilke, Stephen K. ; Youngman, Randall E. ; Alrubkhi, Abdulrahman ; Weber, Richard ( April 2024 , Optical Materials Express)

   Erbium lanthanum titanate glasses were prepared by levitation melting for the spectroscopic study of ways to promote the mid-infrared fluorescence. Two series of heavily erbium doped glasses (15 wt%) were prepared with the addition of either Pr³⁺or Nd³⁺in amounts relative to Er³⁺of 0.05, 0.1, and 0.2. Both ions quench the lower Er³⁺laser level with the Pr³⁺doing so more rapidly. Although high co-dopant concentrations result in higher energy transfer, as clearly evidenced in upconversion and downconversion fluorescence measurements, the mid-infrared lifetime also suffers a reduction and, therefore, a balance must be struck in the co-dopant concentration. Lifetime and spectral measurements indicate that, at a fixed relative co-dopant amount, Pr³⁺is more effective than Nd³⁺at removing the bottleneck of the Er^3+ 4I_13/2level. Moreover, consideration of the lifetimes alongside the absorption data of the individual ions indicates that despite the large absorption cross-section of Nd³⁺at 808 nm, the concentration needed to yield more absorbed power than utilizing direct 976 nm excitation of Er³⁺results in unfavorable lifetimes of the mid-infrared transition. In the end, Pr³⁺prevails as the superior co-dopant in terms of the effects on fluorescence lifetimes as well as potential laser system design considerations. In a unique self-doping approach, a reducing melt atmosphere of Ar instead of O₂creates a small fraction of Ti³⁺. In 5Er₂O₃-12La₂O₃-83TiO₂glass, the presence of Ti³⁺quenches the⁴I_13/2emission about 2.6 times more than the⁴I_11/2when lifetimes are compared to an O₂melt environment. As an additional means of increasing the mid-infrared emission, the effect of temperature on the mid- and near- infrared lifetimes of a lightly doped lanthanum titanate composition is investigated between 77-300 K. The mid-infrared lifetime increases by ∼30% while the near-infrared lifetime increases by ∼10%, which suggests in addition to co-doping, active cooling of the gain media will further enhance performance.

    

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5. Statistical (n,$$\gamma $$) cross section model comparison for short-lived nuclei

   https://doi.org/10.1140/epja/s10050-023-00920-0  

   Lewis, R. ; Couture, A. ; Liddick, S. N. ; Spyrou, A. ; Bleuel, D. L. ; Campo, L. Crespo ; Crider, B. P. ; Dombos, A. C. ; Guttormsen, M. ; Kawano, T. ; et al ( March 2023 , The European Physical Journal A)

   Neutron-capture cross sections of neutron-rich nuclei are calculated using a Hauser–Feshbach model when direct experimental cross sections cannot be obtained. A number of codes to perform these calculations exist, and each makes different assumptions about the underlying nuclear physics. We investigated the systematic uncertainty associated with the choice of Hauser-Feshbach code used to calculate the neutron-capture cross section of a short-lived nucleus. The neutron-capture cross section for$$^{73}\hbox {Zn}$$${}^{73}\text{Zn}$(n,$$\gamma $$$\gamma$)$$^{74}\hbox {Zn}$$${}^{74}\text{Zn}$was calculated using three Hauser-Feshbach statistical model codes: TALYS, CoH, and EMPIRE. The calculation was first performed without any changes to the default settings in each code. Then an experimentally obtained nuclear level density (NLD) and$$\gamma $$$\gamma$-ray strength function ($$\gamma \hbox {SF}$$$\gamma \text{SF}$) were included. Finally, the nuclear structure information was made consistent across the codes. The neutron-capture cross sections obtained from the three codes are in good agreement after including the experimentally obtained NLD and$$\gamma \hbox {SF}$$$\gamma \text{SF}$, accounting for differences in the underlying nuclear reaction models, and enforcing consistent approximations for unknown nuclear data. It is possible to use consistent inputs and nuclear physics to reduce the differences in the calculated neutron-capture cross section from different Hauser-Feshbach codes. However, ensuring the treatment of the input of experimental data and other nuclear physics are similar across multiple codes requires a careful investigation. For this reason, more complete documentation of the inputs and physics chosen is important.

    

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