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Electrocatalysts play a key role in accelerating the sluggish electrochemical CO2 reduction (ECR) involving multi‐electron and proton transfer. We now develop a proton capture strategy by accelerating the water dissociation reaction catalyzed by transition‐metal nanoparticles (NPs) adjacent to atomically dispersed and nitrogen‐coordinated single nickel (Ni−Nx) active sites to accelerate proton transfer to the latter for boosting the intermediate protonation step, and thus the whole ECR process. Aberration‐corrected scanning transmission electron microscopy, X‐ray absorption spectroscopy, and calculations reveal that the Ni NPs accelerate the adsorbed H (Had) generation and transfer to the adjacent Ni−Nx sites for boosting the intermediate protonation and the overall ECR processes. This proton capture strategy is universal to design and prepare for various high‐performance catalysts for diverse electrochemical reactions even beyond ECR. [ABSTRACT FROM AUTHOR]

We employ a 2.5D particle‐in‐cell simulation to study a scenario where the reconnection process captures cold streaming protons. As soon as the tailward streaming protons become involved, they contribute to the overall momentum balance, altering the initially symmetric dynamics. Adding tailward‐directed momentum to the reconnection process results in a tailward propagation of the reconnection site. We investigate how the reconnection process reorganizes itself due to the changing momentum conditions on the kinetic scale and how the reconnection rate is affected. We find that adding tailward momentum does not result in a significantly different reconnection rate compared to the case without cold streaming protons, when scaled to the total Alfvén velocity. This implies that the effect of changing inflow conditions due to the motion of the reconnection site appears to be minimal. The dynamics of the particles are, however, significantly different depending on whether they enter on the tailward or Earthward side of the reconnection site. On the Earthward side they are reflected and thermalized, while on the tailward side they are picked up and accelerated. The cold proton density and Ez on the Earthward side are turbulent, while the tailward side has laminar cold proton density striations and an embedded Ez layer. Also, since the initial plasma sheet population is swept up on one side and flushed out on the other, asymmetries in the densities and strength of Hall fields emerge. Our results are important for understanding the development and dynamics of magnetospheric substorms and storms. Key Points: Cold streaming protons flowing aligned with the upstream magnetic field cause the X line to move at the total mass velocityThe reconnection rate is unaffected by the streaming velocityOn the tailward side Ez remains laminar, whereas the Ez structure broadens and protons become more thermalized at the Earthward side [ABSTRACT FROM AUTHOR]

We investigate the two-proton capture reaction of the prominent rapid proton capture waiting point nucleus, 68 Se, that produces the borromean nucleus 70 Kr ( Se 68 + p + p ). We apply a recently formulated general model where the core nucleus, 68 Se, is treated in the mean-field approximation and the three-body problem of the two valence protons and the core is solved exactly. We compare using two popular Skyrme interactions, SLy4 and SkM*. We calculate E 2 electromagnetic two-proton dissociation and capture cross sections, and derive the temperature dependent capture rates. We vary the unknown 2 + resonance energy without changing any of the structures computed self-consistently for both core and valence particles. We find rates increasing quickly with temperature below 2–4 GK after which we find rates varying by about a factor of two independent of 2 + resonance energy. The capture mechanism is sequential through the f 5 / 2 proton-core resonance, but the continuum background contributes significantly. [ABSTRACT FROM AUTHOR]

We present the results of determinations of age, helium abundance (Y), metallicity ([Fe/H]), and estimations of abundances of the elements: C, N, O, Mg, Ca, Ti, Cr, Ni, Sr, and Ba of four globular clusters in the neighborhood of the Andromeda galaxy ([SD2009]GC7,Mayall II, Mackey-GC1 (MGC1), and Bol 298 (MGC6)) and of six Galactic clusters. Medium-resolution long-slit integrated-light spectra from the clusters under study were used to determine the parameters.Observations of extra-galactic objects were carried out with the 6-m SAO RAS telescope using the SCORPIO-1 multimode focal reducer. Galactic globular clusters NGC6341 (M92), NGC6838 (M71), and NGC7078 were observed with the CARELEC spectrograph at the 1.93-m telescope of the Haute-Provence Observatory. The integratedlight spectra of Galactic globular clusters NGC104, NGC6121 (M4), and NGC7078 (M15) were taken from the spectral library by Schiavon.We selected the best isochrone for each cluster by comparison of the shapes and intensities of the observed and theoretical Balmer line profiles. [ABSTRACT FROM AUTHOR]

A critical issue in the asymptotic giant branch (AGB) self-enrichment scenario for the formation of multiple populations in globular clusters (GCs) is the inability to reproduce the magnesium isotopic ratios, despite the model in principle can account for the depletion of magnesium. In this work, we analyse how the uncertainties on the various p-capture cross sections affect the results related to the magnesium content of the ejecta of AGB stars. The observed distribution of the magnesium isotopes and of the overall Mg-Al trend in M13 and NGC 6752 are successfully reproduced when the proton-capture rate by 25Mg at the temperatures ~100 MK, in particular the 25Mg(p, γ)26Alm channel, is enhanced by a factor ~3 with respect to the most recent experimental determinations. This assumption also allows us to reproduce the full extent of the Mg spread and the Mg-Si anticorrelation observed in NGC 2419. The uncertainties in the rate of the 25Mg(p, γ)26Alm reaction at the temperatures of interest here leave space for our assumption and we suggest that new experimental measurements are needed to settle this problem. We also discuss the competitive model based on the supermassive star nucleosynthesis. [ABSTRACT FROM AUTHOR]

Certain astrophysical environments such as thermonuclear outbursts on accreting neutron stars (Type-I X-ray bursts) are hot enough to allow for breakout from the Hot CNO hydrogen burning cycles to the rapid proton capture (rp) process. An important breakout reaction sequence is 15 O( α , γ ) 19 Ne(p, γ ) 20 Na and the 19 Ne(p, γ ) 20 Na reaction rate is expected to be dominated by a single resonance at 457 keV above the proton threshold in 20 Na. The resonance strength and, hence, reaction rate depends strongly on whether this 20 Na state at an excitation energy of 2647 keV has spin and parity of 1 + or 3 + . Previous 20 Mg ( J π = 0 + ) β + decay experiments have relied almost entirely on searches for β -delayed proton emission from this resonance in 20 Na to limit the log ft value and, hence, J π . However there is a non-negligible γ -ray branch expected that must also be limited experimentally to determine the log ft value and constrain J π . We have measured the β -delayed γ decay of 20 Mg to complement previous β -delayed proton decay work and provide the first complete limit based on all energetically allowed decay channels through the 2647 keV state. Our limit confirms that a 1 + assignment for this state is highly unlikely. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the sensitivities of positron decays on a one-zone model of type-I X-ray bursts. Most existing studies have multiplied or divided entire beta decay rates (electron captures and beta decay rates) by 10. Instead of using the standard Fuller & Fowler (FFNU) rates, we used the most recently developed weak library rates [1] , which include rates from Langanke et al.'s table (the LMP table) (2000) [2] , Langanke et al.'s table (the LMSH table) (2003) [3] , and Oda et al.'s table (1994) [4] (all shell model rates). We then compared these table rates with the old FFNU rates [5] to study differences within the final abundances. Both positron decays and electron capture rates were included in the tables. We also used pn -QRPA rates [6,7] to study the differences within the final abundances. Many of the positron rates from the nuclei's ground states and initial excited energy states along the rapid proton capture ( rp ) process have been measured in existing studies. However, because temperature affects the rates of excited states, these studies should have also acknowledged the half-lives of the nuclei's excited states. Thus, instead of multiplying or dividing entire rates by 10, we studied how the half-lives of sensitive nuclei in excited states affected the abundances by dividing the half-lives of the ground states by 10, which allowed us to set the half-lives of the excited states. Interestingly, we found that the peak of the final abundance shifted when we modified the rates from the excited states of the 105 Sn positron decay rates. Furthermore, the abundance of 80 Zr also changed due to usage of pn -QRPA rates instead of weak library rates (the shell model rates). [ABSTRACT FROM AUTHOR]

We considered one of the proton halo nuclei candidates, 13 N * nucleus, and calculated the cross section and astrophysical S-factor for 12 C ( p, γ ) 13 N * reaction using halo effective field theory without pion (hEFT ¬ π ). The halo effective field theory is used to examine the halo nucleus bound state with a large S-wave scattering length. We calculated the radiative proton capture cross section and the astrophysical S-factor from the fields of the core and the valence proton at the Leading-Order (LO). We showed that there is a good agreement among the our results for cross section and astrophysical S-factor of the 12 C ( p, γ ) 13 N * reaction and the experimental data. The astrophysical S-factor that has been estimated at the zero energy ( E cm =0) by using a theoretical calculation of the cross section for direct radiative capture and an extrapolation of this calculation obtained S ( 0 ) = 1.883 × 10 − 3 MeV-b. [ABSTRACT FROM AUTHOR]

Converting light into chemical energy often occurs through redox reactions that require transfer of several electrons and protons. Using light to control proton transfer has the potential for driving otherwise unfavorable protonation reactions or producing transient pH changes. Photoacids and photobases are fundamental functional elements that could serve this purpose. Previously, we have reported the thermodynamic drive for proton removal in a series of quinoline photobases using Forster cycle analysis of the singlet states. Because the existence of thermodynamic drive does not imply that the molecules can indeed capture protons in the excited state, in this work we report the kinetics of proton removal from water by 5-R-quinolines, R = {NH2, OCH3, H, Cl, Br, CN}, using ultrafast transient absorption spectroscopy. We found that the time constants and mechanisms of proton capture from water are highly sensitive to the substituent. In some cases, proton transfer occurs within the singlet manifold, whereas in some others intersystem crossing competes with this process. We have evidence that the triplet states are also capable of proton capture in two of the compounds. This renders the excited state proton transfer process more complicated than can be captured by the linear free energy relationships inferred from the energetics of the singlet states. We have measured proton capture times in this family to be in the range of several tens of picoseconds with no discernible trend with respect to the Hammett parameter of the substituents. This wide range of mechanisms is attributed to the high density of excited electronic states in the singlet and triplet manifolds. The ordering between these states is expected to change by substituent, solvent, and hydrogen bonding, thus making the rate of intersystem crossing and proton transfer very sensitive to these parameters. These results are necessary fundamental steps to assess the capabilities of photobases in prospective applications such as photomediated proton removal in redox reactions, steady state optical regulation of local pH, and pOH jump kinetics experiments. [ABSTRACT FROM AUTHOR]

The effects of confinement of transition states and bound intermediates are described here based on kinetic and theoretical studies for Prins condensation and oligomerization reactions of isobutanal-isobutene reactant mixtures catalyzed by Brønsted acid sites of similar strength but confined within diverse microporous (TON, BEA, MFI, FAU) and mesoporous (Al-MCM-41) aluminosilicate structures. Kinetic data and density functional theory (DFT) show that smaller voids lead to more stable bound monomers derived from isobutene and isobutanal and to protons nearly saturated with H-bonded isobutanal. Prins condensation forms 2,5-dimethyl-hexadiene regioisomers (2,5-DMH) with rate constants that reflect the different stability of the kinetically-relevant C C bond formation transition states and their H-bonded isobutanal precursors. Their differences in size lead to reactivities that depend sensitively on the size and shape of the confining voids in each aluminosilicate and even on the location of the Al-atoms (and the protons) within a given framework. Specifically, FAU leads to the highest turnover rates, because larger voids in Al-MCM-41 form less effective van der Waals contacts with the transition state, while the smaller voids within TON and BEA lead to enthalpic and entropic penalties brought forth by host-guest distortions. MFI cage-like intersections provide more effective stabilization than BEA cylindrical channels of similar size and lead to higher turnover rates and smaller DFT-derived activation free energies; these subtle effects of void shape on reactivity are neglected in descriptions of the confining frameworks based on spherical constructs. Reactivity descriptors require instead theoretical treatments that rigorously account for van der Waals interactions and for the entropy losses and host-guest distortions required for confinement, as reported here from confinement free energies ensemble-averaged over all crystallographic locations in each aluminosilicate structure. The ratios of rate constants for these parallel isobutene dimerization and Prins condensation reactions depend only weakly on the nature of the aluminosilicate framework, because of the similar size and shape of their respective transition states and bound precursors. Transition states for secondary skeletal isomerization and cyclization of 2,5-DMH condensation products, however, are stabilized more effectively (relative to condensation transition states) within voids of intermediate size (BEA, MFI), leading to higher selectivity to secondary products. MFI cage-like structures specifically catalyze the conversion of 2,5-DMH to cyclic 1,4-dimethyl-cyclohexene isomers, direct precursors to p -xylene, with unique specificity. [ABSTRACT FROM AUTHOR]

The possibility of formation of moving exotic protonium atoms at channeling of antiprotons in an ionic crystal of lithium hydride is proposed and investigated. For this purpose the probability of proton capture by moving antiprotons channeling in crystallographic H − –(1 1 1) planes and H − –(1 1 0) axes in ionic LiH crystal was calculated. It has been shown that the process of formation of moving exotic pp – protonium atoms regarding antiprotons velocities has a resonance character depending on quantum states of these protonium atoms. It was shown that at the capture to higher quantum states the magnitude of resonance peaks increases and the resonance velocities decreases. [ABSTRACT FROM AUTHOR]

The future frontier of the Isotope Separation On-Line (ISOL) method is to increase the intensity of the Radioactive Isotope Beams (RIB) by many orders of magnitude in order to satisfy challenging experiments such as Rn-Electric Dipole Moment, Fr-Parity Non Conservation… and in general for radiative proton-capture relevant for nuclear astrophysics processes. The most direct method to obtain higher RIB intensity is to increase the driver beam intensity. New techniques were developed such as composite targets, where the target material is deposited onto a high thermal conductive substrate allowing a better heat dissipation. Combined with high-power target using radial finned for radiative cooling, these targets are capable of dissipating up to 20 kW depending on the target material operating temperature. Another method to increase RIB intensity is the use of indirect ISOL method, where secondary particle beam (n or γ ) interacts with a fissile target material. By decoupling the power deposition in the system composed of a converter and ISOL target allows for much higher primary beam power. Indirect ISOL-target method permit reach several hundred of kW to MW of driver beam power, allowing the production of intense fission products beams. This paper reviews the thick ISOL target approach for producing intense radioactive ion beams. [ABSTRACT FROM AUTHOR]

We analyze the effects of finite-range corrections in halo effective field theory for S-wave proton halo nuclei. We calculate the charge radius to next-to-leading order and the astrophysical S -factor for low-energy proton capture to fifth order in the low-energy expansion. As an application, we confront our results with experimental data for the S -factor for proton capture on Oxygen-16 into the excited 1 / 2 + state of Fluorine-17. Our low-energy theory is characterized by a systematic low-energy expansion, which can be used to quantify an energy-dependent model error to be utilized in data fitting. Finally, we show that the existence of proton halos is suppressed by the need for two fine tunings in the underlying theory. [ABSTRACT FROM AUTHOR]

The Galactic Archaeology with HERMES (GALAH) survey is a large high-resolution spectro-scopic survey using the newly commissioned High Efficiency and Resolution Multi-Element Spectrograph (HERMES) on the Anglo-Australian Telescope. The HERMES spectrograph provides high-resolution (R ~ 28 000) spectra in four passbands for 392 stars simultaneously over a 2 deg field of view. The goal of the survey is to unravel the formation and evolution-ary history of the Milky Way, using fossil remnants of ancient star formation events which have been disrupted and are now dispersed throughout the Galaxy. Chemical tagging seeks to identify such dispersed remnants solely from their common and unique chemical signatures; these groups are unidentifiable from their spatial, photometric or kinematic properties. To carry out chemical tagging, the GALAH survey will acquire spectra for a million stars down to V ~ 14. The HERMES spectra of FGK stars contain absorption lines from 29 elements including light proton-capture elements, a-elements, odd-Z elements, iron-peak elements and n-capture elements from the light and heavy s-process and the r-process. This paper describes the motivation and planned execution of the GALAH survey, and presents some results on the first-light performance of HERMES. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with forbidden states, the possibility of describing the available experimental data for the total cross sections and astrophysical S-factor of the reaction of pB capture to the ground state of the С nucleus at astrophysical energies is considered. [ABSTRACT FROM AUTHOR]

Low-energy proton capture reactions have been studied in a statistical model using the semimicroscopic optical potential in the mass range A=110-125. Nuclear density obtained from relativistic mean-field calculations has been folded with nucleon-nucleon interactions to obtain the optical potential. Theoretical results have been compared with experimental measurements to normalize the potential. Results have also been compared with a standard calculation available in the literature. [ABSTRACT FROM AUTHOR]

We formulate the Gamow shell model (GSM) in coupled-channel (CC) representation for the description of proton/neutron radiative capture reactions and present the first application of this new formalism for the calculation of cross sections in mirror reactions 7Be(p,γ)s8 and 7Li(n,γ)8Li. The GSM-CC formalism is applied to a translationally invariant Hamiltonian with an effective finite-range two-body interaction. Reactions channels are built by GSM wave functions for the ground state 3/2- and the first excited state 1/2- of 7Be/7Li and the proton/neutron wave function expanded in different partial waves. [ABSTRACT FROM AUTHOR]

Low-energy proton capture reactions in the mass 55-60 region are studied in a microscopic optical model. The nuclear density profile is calculated using the relativistic mean field theory. The DDM3Y interaction is folded with the theoretical density to obtain the proton-nucleus optical potential. A definite set of normalization parameters has been obtained for the concerned mass region by comparing with all available experimental data in this mass region. These parameters have been used to obtain proton capture rates for astrophysically important reactions in this mass region. [ABSTRACT FROM AUTHOR]

The slow β -decay of the 68 Se waiting point in the astrophysical rp-process can in principle be bypassed by a sequential two proton capture. The rate of this reaction sequence depends exponentially on the 69 Br proton separation energy. We studied β -delayed proton emission of 69 Kr and extracted a proton separation energy of − 641 ( 42 ) keV . In addition, we determined a 69 Kr β -decay half-life of T 1 / 2 = 28 ( 1 ) ms and an excitation energy of 3153(55) keV of the 69 Kr isobaric analog state in 69 Br. X-ray burst model calculations show that regardless of the values of other uncertain masses in the region, the new S p ( Br 69 ) allows for a reaction flow via Se 68 ( 2 p , γ ) of at most 20%. Uncertainties are sufficiently reduced to conclude that Se 68 ( 2 p , γ ) has at best a very small effect on burst light curve and composition, and that 68 Se is a strong rp-process waiting point. Our results also exclude the possibility of a suggested longer lived, so far unobserved, 69 Br ground state. [ABSTRACT FROM AUTHOR]