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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Zn2H18Cl4O9 by Materials Project

Zn(H2O)6ZnCl4(H2O)3 is alpha Pu-derived structured and crystallizes in the orthorhombic P2_12_12_1 space group. The structure is zero-dimensional and consists of twelve water molecules, four ZnCl4 clusters, and four zinc hexahydrate molecules. In each ZnCl4 cluster, Zn2+ is bonded in a tetrahedral geometry to four Cl1- atoms. There are a spread of Zn–Cl bond distances ranging from 2.28–2.31 Å. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Zn2+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Zn2+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Zn2+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one Zn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UH12(NO7)2 by Materials Project

UH4(NO5)2(H2O)4 is alpha Pu-derived structured and crystallizes in the orthorhombic Cmc2_1 space group. The structure is zero-dimensional and consists of sixteen water molecules and four UH4(NO5)2 clusters. In each UH4(NO5)2 cluster, U6+ is bonded in a distorted linear geometry to eight O2- atoms. There are a spread of U–O bond distances ranging from 1.80–2.57 Å. There are two inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.24 Å) and two longer (1.28 Å) N–O bond length. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.25 Å) and two longer (1.27 Å) N–O bond length. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a distorted single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one N5+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one U6+ and one N5+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one U6+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one U6+ atom. In the fifth O2- site, O2- is bonded in a distorted water-like geometry to one U6+ and two H1+ atoms. In the sixth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ir(N3O4)3 by Materials Project

(Ir(NO2)6)2(N2)3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is zero-dimensional and consists of twelve ammonia molecules and four Ir(NO2)6 clusters. In each Ir(NO2)6 cluster, Ir3+ is bonded in a cuboctahedral geometry to twelve equivalent O2- atoms. All Ir–O bond lengths are 2.26 Å. N+2.33+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All N–O bond lengths are 1.95 Å. O2- is bonded in a 3-coordinate geometry to one Ir3+ and two equivalent N+2.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ReN(OF2)3 by Materials Project

ReOF6NO2 is alpha Pu-derived structured and crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of eight hydroxylamine, n-hydroxy- molecules and eight ReOF6 clusters. In each ReOF6 cluster, Re7+ is bonded in a pentagonal bipyramidal geometry to one O2- and six F1- atoms. The Re–O bond length is 1.71 Å. There are a spread of Re–F bond distances ranging from 1.92–1.97 Å. O2- is bonded in a single-bond geometry to one Re7+ atom. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Re7+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Re7+ atom. In the third F1- site, F1- is bonded in a distorted single-bond geometry to one Re7+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Re7+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one Re7+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one Re7+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiH18C2N8(OF3)2 by Materials Project

(CN4H7)2SiF6(H2O)2 is alpha Pu-derived structured and crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two aminoguanidinium molecules, two water molecules, and one SiF6 cluster. In the SiF6 cluster, Si4+ is bonded in an octahedral geometry to six F1- atoms. There is four shorter (1.72 Å) and two longer (1.73 Å) Si–F bond length. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Si4+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Si4+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiSi4H27(C3O)3 by Materials Project

LiSi3H27(C3O)3Si is alpha carbon monoxide-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four silicon molecules and four LiSi3H27(C3O)3 clusters. In each LiSi3H27(C3O)3 cluster, Li1+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is one shorter (1.99 Å) and two longer (2.00 Å) Li–O bond length. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded in a trigonal non-coplanar geometry to two C4- and one O2- atom. Both Si–C bond lengths are 1.89 Å. The Si–O bond length is 1.73 Å. In the second Si4+ site, Si4+ is bonded in a trigonal non-coplanar geometry to two C4- and one O2- atom. Both Si–C bond lengths are 1.89 Å. The Si–O bond length is 1.73 Å. In the third Si4+ site, Si4+ is bonded in a trigonal non-coplanar geometry to two C4- and one O2- atom. Both Si–C bond lengths are 1.89 Å. The Si–O bond length is 1.73 Å. There are nine inequivalent C4- sites. In the first C4- site, C4- is bonded in a tetrahedral geometry to three H+0.93+ and one O2- atom. All C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. In the second C4- site, C4- is bonded in a tetrahedral geometry to three H+0.93+ and one O2- atom. All C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. In the third C4- site, C4- is bonded in a tetrahedral geometry to three H+0.93+ and one O2- atom. All C–H bond lengths are 1.10 Å. The C–O bond length is 1.43 Å. In the fourth C4- site, C4- is bonded to one Si4+ and three H+0.93+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the fifth C4- site, C4- is bonded to one Si4+ and three H+0.93+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the sixth C4- site, C4- is bonded to one Si4+ and three H+0.93+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the seventh C4- site, C4- is bonded to one Si4+ and three H+0.93+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the eighth C4- site, C4- is bonded to one Si4+ and three H+0.93+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the ninth C4- site, C4- is bonded to one Si4+ and three H+0.93+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. There are twenty-seven inequivalent H+0.93+ sites. In the first H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the second H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the third H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the fourth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the fifth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the sixth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the seventh H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the eighth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the ninth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the tenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the eleventh H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twelfth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the thirteenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the fourteenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the fifteenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the sixteenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the seventeenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the eighteenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the nineteenth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twentieth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twenty-first H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twenty-second H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twenty-third H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twenty-fourth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twenty-fifth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twenty-sixth H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. In the twenty-seventh H+0.93+ site, H+0.93+ is bonded in a single-bond geometry to one C4- atom. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Si4+, and one C4- atom. In the second O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Si4+, and one C4- atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Si4+, and one C4- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SbI3Cl8 by Materials Project

Sb(ICl4)2I is alpha Niobium phosphide-like structured and crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of one hydriodic acid molecule and one Sb(ICl4)2 cluster. In the Sb(ICl4)2 cluster, Sb5+ is bonded in an octahedral geometry to six Cl1- atoms. There are a spread of Sb–Cl bond distances ranging from 2.38–2.51 Å. I1+ is bonded in a linear geometry to two Cl1- atoms. There are one shorter (2.39 Å) and one longer (2.82 Å) I–Cl bond lengths. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Sb5+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one I1+ atom. In the third Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one Sb5+ and one I1+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one Sb5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

In-orbit performance of the soft X-ray imaging telescope Xtend aboard XRISM

Here, we present a summary of the in-orbit performance of the soft X-ray imaging telescope Xtend onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), based on in-flight observation data, including first-light celestial objects, calibration sources, and results from the cross-calibration campaign with other currently operating X-ray observatories. XRISM/Xtend has a large field of view of ${38{^{\prime }_{.}}5}$ $\times$ ${38{^{\prime }_{.}}5}$, covering an energy range of 0.4–13 keV, as demonstrated by the first-light observation of the galaxy cluster Abell 2319. It also features an energy resolution of 170–180 eV at 6 keV, which meets the mission requirement and enables us to resolve He-like and H-like Fe K$\alpha$ lines. Throughout the observation during the performance verification phase, we confirm that two issues identified in the Soft X-ray Imager (SXI) onboard the previous Hitomi mission—light leakage and crosstalk events—are addressed and suppressed in the case of Xtend. A joint cross-calibration observation of the bright quasar 3C 273 results in an effective area measured to be $\sim$420 cm$^{2}$ at1.5 keV and $\sim$310 cm$^{2}$ at 6.0 keV, which matches values obtained in ground tests. We also continuously monitor the health of Xtend by analyzing overclocking data, calibration source spectra, and day-Earth observations; the readout noise is stable and low, and contamination is negligible even one year after launch. A low background level compared with other major X-ray instruments onboard satellites, combined with the largest grasp ($\Omega _{\rm eff}\sim 60$ cm$^2$ deg$^2$) of Xtend, will not only support Resolve analysis, but also enable significant scientific results on its own. This includes near-future follow-up observations and transient searches in the context of time-domain and multi-messenger astrophysics.

instrumentation: detectors: Xtend↗
DOE OSTI2020

Materials Data on TeS4(NCl)4 by Materials Project

(NS)4TeCl4 is alpha carbon monoxide-like structured and crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of four 1,3,5,7,2,4,6,8-tetrathiatetrazocane molecules and four TeCl4 clusters. In each TeCl4 cluster, Te4+ is bonded in a distorted rectangular see-saw-like geometry to four Cl1- atoms. There are a spread of Te–Cl bond distances ranging from 2.48–2.54 Å. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom. In the third Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Te4+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Resonant scattering at the center of the galaxy cluster PKS 0745-191 with XRISM

We report evidence of the resonant scattering effect at the center of the galaxy cluster PKS 0745-191 with XRISM. We analyzed XRISM/Resolve commissioning-phase observations of the distant cluster PKS 0745-191 ($z = 0.103$) with a $54$ ks exposure. The gain drift was corrected using the onboard modulated X-ray source (MXS), and spectra were extracted from all the pixels that were well illuminated by MXS, the core region (four central pixels, $\sim$100 kpc), and the surrounding region. A single-temperature collisional ionization equilibrium (CIE) model fits the full field-of-view spectrum with $kT \approx 6$ keV and a turbulent velocity of ${\approx}120$ km s$^{-1}$. From the core ($r < 50$ kpc) spectrum, we detected a ${\approx}22\%$ suppression of the Fe xxv He$\alpha$ resonance (w) line relative to the CIE prediction. We performed a Monte Carlo simulation to calculate the resonant scattering (RS) effect using radial profiles from Chandra data. The RS-inferred turbulence agrees with that by Resolve line-broadening, demonstrating that RS provides an independent and consistent constraint on ICM turbulence. These results highlight XRISM/Resolve’s potential for turbulence studies in galaxy clusters.

Astronomy and AstroPhysics↗
DOE OSTI2023

Compressing the Cosmological Information in One-dimensional Correlations of the Lyman-$\alpha$ Forest

Observations of the Lyman-α forest from spectroscopic surveys such as the Baryon Oscillation Spectroscopic Survey or its extension, eBOSS, or the ongoing Dark Energy Spectroscopic Instrument (DESI) survey offer a unique window to study the growth of structure on megaparsec scales. Interpretation of these measurements is a complicated task, requiring hydrodynamical simulations to model and marginalize over the thermal and ionization state of the intergalactic medium. This complexity has limited the use of Lyα clustering measurements in joint cosmological analyses. In this work we show that the cosmological information content of the one-dimensional power spectrum (P 1D ) of the Lyman-α forest can be compressed into a simple two-parameter likelihood without any significant loss of constraining power. We simulate P 1D measurements from DESI using hydrodynamical simulations and show that the compressed likelihood is model independent and lossless, recovering unbiased results even in the presence of massive neutrinos or running of the primordial power spectrum.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The 3D Kinematics of the Orion Nebula Cluster: NIRSPEC-AO Radial Velocities of the Core Population

The kinematics and dynamics of stellar and substellar populations within young, still-forming clusters provide valuable information for constraining theories of formation mechanisms. Using Keck II NIRSPEC+AO data, we have measured radial velocities for 56 low-mass sources within 4' of the core of the Orion Nebula Cluster (ONC). We also remeasure radial velocities for 172 sources observed with SDSS/APOGEE. These data are combined with proper motions measured using HST ACS/WFPC2/WFC3IR and Keck II NIRC2, creating a sample of 135 sources with all three velocity components. The velocities measured are consistent with a normal distribution in all three components. We measure intrinsic velocity dispersions of (${\sigma }_{{v}_{\alpha }}$, ${\sigma }_{{v}_{\delta }}$, ${\sigma }_{{v}_{r}}$) = (1.64 ± 0.12, 2.03 ± 0.13, ${2.56}_{-0.17}^{+0.16}$) km s –1 . Our computed intrinsic velocity dispersion profiles are consistent with the dynamical equilibrium models from Da Rio et al. (2014) in the tangential direction but not in the line-of-sight direction, possibly indicating that the core of the ONC is not yet virialized, and may require a nonspherical potential to explain the observed velocity dispersion profiles. We also observe a slight elongation along the north–south direction following the filament, which has been well studied in previous literature, and an elongation in the line-of-sight to tangential velocity direction. These 3D kinematics will help in the development of realistic models of the formation and early evolution of massive clusters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

The Hoyle Family: The Search for Alpha-Condensate States in Light Nuclei

Our present understanding of the structure of the Hoyle state in 12 C and other near-threshold states in α-conjugate nuclei is reviewed in the framework of the α-condensate model. The 12 C Hoyle state, in particular, is a candidate for α-condensation, due to its large radius and α-cluster structure. The predicted features of nuclear α-particle condensates are reviewed along with a discussion of their experimental indicators, with a focus on precision break-up measurements. Two experiments are discussed in detail, firstly concerning the break-up of 12 C and then the decays of heavier nuclei. With more theoretical input, and increasingly complex detector setups, precision break-up measurements can, in principle, provide insight into the structures of states in α-conjugate nuclei. However, the commonly-held belief that the decay of a condensate state will result in Nα-particles is challenged. We further conclude that unambiguously characterizing excited states built on α-condensates is difficult, despite improvements in detector technology.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

The lessons learned from ephemeral nuclei

Recent experimental analyses of fleeting clusters of protons and neutrons put the very notion of the atomic nucleus in a new light.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

A detailed chemical study of the extreme velocity stars in the galaxy

ABSTRACT Two decades on, the study of hypervelocity stars is still in its infancy. These stars can provide novel constraints on the total mass of the Galaxy and its dark matter distribution. However how these stars are accelerated to such high velocities is unclear. Various proposed production mechanisms for these stars can be distinguished using chemo-dynamic tagging. The advent of Gaia and other large surveys have provided hundreds of candidate hyper velocity objects to target for ground-based high-resolution follow-up observations. We conduct high-resolution spectroscopic follow-up observations of 16 candidate late-type hyper velocity stars using the Apache Point Observatory and the McDonald Observatory. We derive atmospheric parameters and chemical abundances for these stars. We measure up to 22 elements, including the following nucleosynthetic families: $\alpha$ (Mg, Si, Ca, and Ti), light/odd-Z (Na, Al, V, Cu, and Sc), Fe-peak (Fe, Cr, Mn, Co, Ni, and Zn), and neutron capture (Sr, Y, Zr, Ba, La, Nd, and Eu). Our kinematic analysis shows one candidate is unbound, two are marginally bound, and the remainder are bound to the Galaxy. Finally, for the three unbound or marginally bound stars, we perform orbit integration to locate possible globular cluster or dwarf galaxy progenitors. We do not find any likely candidate systems for these stars and conclude that the unbound stars are likely from the the stellar halo, in agreement with the chemical results. The remaining bound stars are all chemically consistent with the stellar halo as well.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Massive neutrinos and degeneracies in Lyman-alpha forest simulations

Using a suite of hydrodynamical simulations with cold dark matter, baryons, and neutrinos, we present a detailed study of the effect of massive neutrinos on the 1-D and 3-D flux power spectra of the Lyman-α (Lyα) forest. The presence of massive neutrinos in cosmology induces a scale- and time-dependent suppression of structure formation that is strongest on small scales. Measuring this suppression is a key method for inferring neutrino masses from cosmological data, and is one of the main goals of ongoing and future surveys like eBOSS, DES, LSST, Euclid or DESI . The clustering in the Lyα forest traces the quasi-linear power at late times and on small scales. In combination with observations of the cosmic microwave background, the forest therefore provides some of the tightest constraints on the sum of the neutrino masses. However there is a well-known degeneracy between Σmν and the amplitude of perturbations in the linear matter power spectrum. We study the corresponding degeneracy in the 1-D flux power spectrum of the Lyα forest, and for the first time also study this degeneracy in the 3-D flux power spectrum. We show that the non-linear effects of massive neutrinos on the Lyα forest, beyond the effect of linear power amplitude suppression, are negligible, and this degeneracy persists in the Lyα forest observables to a high precision. Here, we discuss the implications of this degeneracy for choosing parametrisations of the Lyα forest for cosmological analysis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Modeling of the high column density systems in the Lyman-Alpha forest

The Lyman-α forests observed in the spectra of high-redshift quasars can be used as a tracer of the cosmological matter density to study baryon acoustic oscillations (BAO) and the Alcock-Paczynski effect. Extraction of cosmological information from these studies requires modeling of the forest correlations. While the models depend most importantly on the bias parameters of the intergalactic medium (IGM), they also depend on the numbers and characteristics of high-column-density systems (HCDs) ranging from Lyman-limit systems with column densities log N HI /1cm -2 > 17 to damped Lyman-α systems (DLAs) with log N HI /1cm -2 > 20.2. These HCDs introduce broad damped absorption characteristic of a Voigt profile. Consequently they imprint a component on the power spectrum whose modes in the radial direction are suppressed, leading to a scale-dependent bias. Using mock data sets of known HCD content, we test a model that describes this effect in terms of the distribution of column densities of HCDs, the Fourier transforms of their Voigt profiles and the bias of the halos containing the HCDs. Our results show that this physically well-motivated model describes the effects of HCDs with an accuracy comparable to that of the ad-hoc models used in published forest analyses. We also discuss the problems of applying the model to real data, where the HCD content and their bias is uncertain.

Lyman alpha forest↗
DOE OSTI2021

The $^3$He+$^5$He$\rightarrow $ $\alpha $+$\alpha $ reaction below the Coulomb barrier via the Trojan Horse Method

For the first time in an application to nuclear astrophysics, a process induced by the unstable 5 He = ( 4 He-n) nucleus, the 3 He+ 5 He→2α reaction, has been studied through the Trojan Horse Method (THM). For that purpose, the quasi-free (QF) contribution of the 9 Be( 3 He,αα) 4 He reaction was selected at E 3 He =4 MeV incident energy. The reaction was studied in a kinematically complete experiment following a recent publication, where for the quasi free contribution the momentum distribution between α and 5 He particle cluster in the 9 Be nucleus in the ground state have been extracted. The angular distribution of the QF 3 He+ 5 He→2α reaction was measured at θ cm = 78°–115°. The energy dependence of the differential cross section of the 3 He+ 5 He→2α virtual reaction was extracted in the energy range E cm = 0–650 keV. In conclusion, the total cross section obtained from the Trojan-horse method was normalized to absolute cross sections from a theoretical calculation in the energy range E cm =300–620 keV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗