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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Multicolor emission from intermediate band semiconductor ZnO 1-x Se x

Photoluminescence and photomodulated reflectivity measurements of ZnOSe alloys are used to demonstrate a splitting of the valence band due to the band anticrossing interaction between localized Se states and the extended valence band states of the host ZnO matrix. A strong multiband emission associated with optical transitions from the conduction band to lower E - and upper E + valence subbands has been observed at room temperature. The composition dependence of the optical transition energies is well explained by the electronic band structure calculated using the kp method combined with the band anticrossing model. The observation of the multiband emission is possible because of relatively long recombination lifetimes. Longer than 1 ns lifetimes for holes photoexcited to the lower valence subband offer a potential of using the alloy as an intermediate band semiconductor for solar power conversion applications.

14 SOLAR ENERGY↗
DOE OSTI2023

Transition metal elements as donor dopants in CdO

CdO has been shown to achieve a high electron concentration N (> 10 21 cm -3 ) and at the same time a high mobility μ (> 100cm 2 /V s) when doped with conventional shallow dopants (In or Ga), and consequently making it a transparent conducting oxide with very low resistivity ρ <10 -4 $\Omega$ cm. In this work, the properties of CdO thin films doped with a series of transition metal elements (CdO:TM) with partially filled 3d and 4d shells, including Sc, Ti, V, Cr, Fe, Y, Mo, and W, were investigated. We find that doping with these TM elements can effectively increase the N in CdO to a maximum N (N max ) of ~(7-12)×10 20 cm -3 with a dopant concentration x max of 4-7 %. However, unlike CdO:In, the μ of CdO:TM films drops rapidly from > 100 to < 10cm 2 /Vs as the dopant concentration x increases, so that they can only achieve a minimum ρ of ~ (1-2) × 10 -4 $\Omega$ cm, ~ a factor of 2-3 higher than that in CdO:In. As a result, free-carrier absorption and plasma reflection effects limit their optical transparency to <1200 nm. For most 3d TM dopants, a qualitatively higher d-donor level E d,donor gives rise to higher E F,max or a higher N max . Although at low x, the optical band gap E opt of CdO:TM follows the calculated values due to free-carrier effects, as x increases, E opt values are significantly higher than the calculated values. This is believed to be an effect of the anticrossing interaction of the localized d-levels and the extended CdO conduction-band (CB) states, giving rise to a lower occupied E - and an upper unoccupied E + subband. In conclusion, the restructured CBs have much flatter dispersion, which also results in a much higher effective mass $m^{\star}_{e}$, hence it can also explain the much lower μ of CdO:TM films with high N.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Study of η′ → π+π−l+l− decays at BESIII

Abstract With a sample of (10087±44)×10 6 J/ψevents accumulated with the BESIII detector, we analyze the decaysη′→ π + π − l + l − (l=e, μ) via the processJ/ψ → γη′. The branching fractions are measured to be$$ \mathcal{B} $$ B (η′→ π + π − e + e − ) = (2.45±0.02(stat.)±0.08(syst.))×10 −3 and$$ \mathcal{B} $$ B (η′→ π + π − μ + μ − ) = (2.16±0.12(stat.)±0.06(syst.))×10 −5 , and the ratio is$$ \frac{\mathcal{B}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{e}^{+}{e}^{-}\right)}{\mathcal{B}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{\mu}^{+}{\mu}^{-}\right)}=113.4\pm 0.9\left(\textrm{stat}.\right)\pm 3.7\left(\textrm{syst}.\right) $$ B η ′ → π + π − e + e − B η ′ → π + π − μ + μ − = 113.4 ± 0.9 stat . ± 3.7 syst . . In addition, by combining theη′ →π + π − e + e − andη′ →π + π − μ + μ − decays, the slope parameter of the electromagnetic transition form factor is measured to beb η′ = 1.30 ± 0.19 (GeV/c 2 ) −2 , which is consistent with previous measurements from BESIII and theoretical predictions from the VMD model. The asymmetry in the angle between theπ + π − andl + l − decay planes, which has the potential to reveal theCP-violation originating from an unconventional electric dipole transition, is also investigated. The asymmetry parameters are determined to be$$ {\mathcal{A}}_{CP}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{e}^{+}{e}^{-}\right)=\left(-0.21\pm 0.73\left(\textrm{stat}.\right)\pm 0.01\left(\textrm{syst}.\right)\right)\% $$ A CP η ′ → π + π − e + e − = − 0.21 ± 0.73 stat . ± 0.01 syst . % and$$ {\mathcal{A}}_{CP}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{\mu}^{+}{\mu}^{-}\right)=\left(0.62\pm 4.71\left(\textrm{stat}.\right)\pm 0.08\left(\textrm{syst}.\right)\right)\% $$ A CP η ′ → π + π − μ + μ − = 0.62 ± 4.71 stat . ± 0.08 syst . % , implying that no evidence ofCP-violation is observed at the present statistics. Finally, an axion-like particle is searched for via the decayη′ →π + π − a, a→e + e − , and upper limits of the branching fractions are presented for the mass assumptions of the axion-like particle in the range of 0−500 MeV/c 2 .

Physics↗
DOE OSTI2021

Nondetection of Helium in the Upper Atmospheres of TRAPPIST-1b, e, and f

We obtained high-resolution spectra of the ultracool M-dwarf TRAPPIST-1 during the transit of its planet “b” using two high-dispersion near-infrared spectrographs, the Infrared Doppler (IRD) instrument on the Subaru 8.2m telescope, and the Habitable Zone Planet Finder (HPF) instrument on the 10 m Hobby–Eberly Telescope. These spectroscopic observations are complemented by a photometric transit observation for planet “b” using the APO/ARCTIC, which assisted us in capturing the correct transit times for our transit spectroscopy. Using the data obtained by the new IRD and HPF observations, as well as the prior transit observations of planets “b,” “e” and “f” from IRD, we attempt to constrain the atmospheric escape of the planet using the He i triplet 10830 Å absorption line. We do not detect evidence for any primordial extended H-He atmospheres in all three planets. To limit any planet-related absorption, we place an upper limit on the equivalent widths of <7.754 mÅ for planet “b,” <10.458 mÅ for planet “e,” <4.143 mÅ for planet “f” at 95% confidence from the IRD data, and <3.467 mÅ for planet “b” at 95% confidence from HPF data. Using these limits along with a solar-like composition isothermal Parker wind model, we attempt to constrain the mass-loss rates for the three planets. For TRAPPIST-1b, our models exclude the highest possible energy-limited rate for a wind temperature <5000 K. This nondetection of extended atmospheres with low mean-molecular weights in all three planets aids in further constraining their atmospheric composition by steering the focus toward the search of high-molecular-weight species in their atmospheres.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

One-electron redox kinetics of aqueous transition metal couples Zn 2+/+ , Co 2+/+ , and Ni 2+/+ using pulse radiolysis

The one-electron redox potentials for aqueous metal couples Co 2+/+ and Ni 2+/+ have been investigated by using pulse radiolysis using their reactions with a series of reference compounds to establish the most positive upper limits of E 0 . Experiments with Zn + were also carried out to confirm the characteristic shape of the expected reduction kinetics. Both formate ions and t-BuOH were employed to scavenge ˙OH radicals and ˙H atoms. Kinetics and fitted first and second order reaction rates have been reported for reactions with methyl viologen, fluorescein, Ru(NH 3 ) 6 3+ , Co(en) 3 2+ , Co(sepulcrate) 3+ , Ru(bpy) 3 2+ , Cr(bpy)33+, and Ni(Me 6 [14]4,11-dieneN4) 2+ . Previous work demonstrated that both Co 2+ and Ni 2+ can be reduced by CO 2 ˙- radicals, giving a negative E 0 limit of -1.9 V vs. SHE. A definite reaction of Ni + with fluorescein di-anions provides a new upper limit of the Ni 2+/+ couple as -0.906 V vs. SHE. The reaction of Co + with Ru(bpy) 3 2+ has been confirmed, giving E 0 = -1.3 V vs. SHE as a rigorous upper limit of the Co 2+/+ couple. In the case of Co 2+/+ , kinetics were complicated by a self-catalyzed metal clustering phenomenon. Initiation rate constants of this process have also been reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Light absorption enhancement of black carbon in a pyrocumulonimbus cloud

Abstract Pyrocumulonimbus (pyroCb) firestorm systems have been shown to inject significant amounts of black carbon (BC) to the stratosphere with a residence time of several months. Injected BC warms the local stratospheric air, consequently perturbing transport and hence spatial distributions of ozone and water vapor. A distinguishing feature of BC-containing particles residing within pyroCb smoke is their thick surface coatings made of condensed organic matter. When coated with non-refractory materials, BC’s absorption is enhanced, yet the absorption enhancement factor ( E abs ) for pyroCb BC is not well constrained. Here, we perform particle-scale measurements of BC mass, morphology, and coating thickness from inside a pyroCb cloud and quantify E abs using an established particle-resolved BC optics model. We find that the population-averaged E abs for BC asymptotes to 2.0 with increasing coating thickness. This value denotes the upper limit of E abs for thickly coated BC in the atmosphere. Our results provide observationally constrained parameterizations of BC absorption for improved radiative transfer calculations of pyroCb events.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Band structure characterization of WS 2 grown by chemical vapor deposition

Growth by chemical vapor deposition (CVD) leads to multilayer WS 2 of very high quality, based on high-resolution angle-resolved photoemission spectroscopy. The experimental valence band electronic structure is considered to be in good agreement with that obtained from density functional theory calculations. We find the spin-orbit splitting at the K¯ point to be 420 ± 20 meV with a hole effective mass of –0.35 ± 0.02 m e for the upper spin-orbit component (the branch closer to the Fermi level) and –0.43 ± 0.07 m e for the lower spin-orbit component. As predicted by theory, a thickness-dependent increase of bandwidth is observed at the top of the valence band, in the region of the Brillouin zone center. In conclusion, the top of the valence band of the CVD-prepared films exhibits a substantial binding energy, consistent with n-type behavior, and in agreement with transistor characteristics acquired using devices incorporating the same WS 2 material.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Improved measurements of the Dalitz decays η / η ′ → γ e + e −

Based on a data sample of 10 billion J / ψ events collected with the BESIII detector, improved measurements of the Dalitz decays η / η ′ → γ e + e − are performed, where the η and η ′ are produced through the radiative decays J / ψ → γ η / η ′ . The branching fractions of η → γ e + e − and η ′ → γ e + e − are measured to be ( 7.07 ± 0.05 ± 0.23 ) × 10 − 3 and ( 4.83 ± 0.07 ± 0.14 ) × 10 − 4 , respectively. Within the single-pole model, the parameter of electromagnetic transition form factor for η → γ e + e − is determined to be Λ η = ( 0.749 ± 0.027 ± 0.007 ) GeV / c 2 . Within the multipole model, we extract the electromagnetic transition form factors for η ′ → γ e + e − to be Λ η ′ = ( 0.802 ± 0.007 ± 0.008 ) GeV / c 2 and γ η ′ = ( 0.113 ± 0.010 ± 0.002 ) GeV / c 2 . The results are consistent with both theoretical predictions and previous measurements. The characteristic sizes of the interaction regions for the η and η ′ are calculated to be ( 0.645 ± 0.023 ± 0.007 ) fm and ( 0.596 ± 0.005 ± 0.006 ) fm , respectively. In addition, we search for the dark photon in η / η ′ → γ e + e − , and the upper limits of the branching fractions as a function of the dark photon are given at 90% confidence level. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2015

Search for B + → ℓ + ν ℓ γ decays with hadronic tagging using the full Belle data sample

We search for the decay B + → ℓ + νℓγ with ℓ + = e + or μ + using the full Belle data set of 772 × 10 6 BB¯ pairs, collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e – collider. We reconstruct one B meson in a hadronic decay mode and search for the B + → ℓ + νℓγ decay in the remainder of the event. Here, we observe no significant signal within the phase space of E$^{sig}_{γ}$ > 1 GeV and obtain upper limits of B(B + → e + ν e γ) < 6.1 × 10 –6 , B(B + → μ + ν μ γ) < 3.4 × 10 –6 , and B(B + → ℓ + ν ℓ γ) < 3.5 × 10 –6 at 90% credibility level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Improved search for heavy neutrinos in the decay π → e ν

In this study, a search for massive neutrinos has been made in the decay π + → e + ν. No evidence was found for extra peaks in the positron energy spectrum indicative of pion decays involving massive neutrinos (π → e + ν h ). Upper limits (90 % C.L.) on the neutrino mixing matrix element |U ei | 2 in the neutrino mass region 60–135 MeV/c 2 were set, which are an order of magnitude improvement over previous results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for lepton flavour violating decays of heavy resonances and quantum black holes to an eμ pair in proton-proton collisions at √s = 8 TeV

A search for narrow resonances decaying to an electron and a muon is presented. The $\mathrm {e}$ ${\mu }$ mass spectrum is also investigated for non-resonant contributions from the production of quantum black holes (QBHs). The analysis is performed using data corresponding to an integrated luminosity of 19.7 $~\text {fb}^\text {-1}$ collected in proton-proton collisions at a centre-of-mass energy of 8 $~\text {TeV}$ with the CMS detector at the LHC. With no evidence for physics beyond the standard model in the invariant mass spectrum of selected $\mathrm {e}\mu $ pairs, upper limits are set at 95 $\%$ confidence level on the product of cross section and branching fraction for signals arising in theories with charged lepton flavour violation. In the search for narrow resonances, the resonant production of a $\mathrm {\tau }$ sneutrino in R-parity violating supersymmetry is considered. The $\mathrm {\tau }$ sneutrino is excluded for masses below 1.28 $~\text {TeV}$ for couplings $\lambda _{132}=\lambda _{231}=\lambda '_{311}=0.01$ , and below 2.30 $~\text {TeV}$ for $\lambda _{132}=\lambda _{231}=0.07$ and $\lambda '_{311}=0.11$ . These are the most stringent limits to date from direct searches at high-energy colliders. In addition, the resonance searches are interpreted in terms of a model with heavy partners of the ${\mathrm {Z}} $ boson and the photon. In a framework of TeV-scale quantum gravity based on a renormalization of Newton’s constant, the search for non-resonant contributions to the $\mathrm {e}$ ${\mu }$ mass spectrum excludes QBH production below a threshold mass $M_{\mathrm {th}}$ of 1.99 $~\text {TeV}$ . In models that invoke extra dimensions, the bounds range from 2.36 $~\text {TeV}$ for one extra dimension to 3.63 $~\text {TeV}$ for six extra dimensions. Furthermore, this is the first search for QBHs decaying into the $\mathrm {e}$ ${\mu }$ final state.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

SPECTRAL LINE SURVEY TOWARD THE YOUNG MASSIVE PROTOSTAR NGC 2264 CMM3 IN THE 4 mm, 3 mm, AND 0.8 mm BANDS

Spectral line survey observations are conducted toward the high-mass protostar candidate NGC 2264 CMM3 in the 4, 3, and 0.8 mm bands with the Nobeyama 45 m telescope and the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope. In total, 265 emission lines are detected in the 4 and 3 mm bands, and 74 emission lines in the 0.8 mm band. As a result, 36 molecular species and 30 isotopologues are identified. In addition to the fundamental molecular species, many emission lines of carbon-chain molecules such as HC{sub 5}N, C{sub 4}H, CCS, and C{sub 3}S are detected in the 4 and 3 mm bands. Deuterated molecular species are also detected with relatively strong intensities. On the other hand, emission lines of complex organic molecules such as HCOOCH{sub 3} and CH{sub 3}OCH{sub 3} are found to be weak. For the molecules for which multiple transitions are detected, rotation temperatures are derived to be 7–33 K except for CH{sub 3}OH. Emission lines with high upper-state energies (E{sub u} > 150 K) are detected for CH{sub 3}OH, indicating the existence of a hot core. In comparison with the chemical composition of the Orion KL, carbon-chain molecules and deuterated molecules are found to be abundant in NGC 2264 CMM3, while sulfur-bearing species and complex organic molecules are deficient. These characteristics indicate the chemical youth of NGC 2264 CMM3 in spite of its location at the center of the cluster forming core, NGC 2264 C.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

ALMA observations of Orion Source I at 350 and 660 GHz

Orion Source I (“SrcI”) is the protostar at the center of the Kleinmann-Low Nebula. ALMA observations of SrcI with 0.″2 angular resolution were made at 350 and 660 GHz to search for the H26α and H21α hydrogen recombination lines and to measure the continuum flux densities. The recombination lines were not detected, ruling out the possibility that SrcI is a hypercompact H ii region. The deconvolved size of the continuum source is approximately 0.″23 × 0.″07 (∼100 × 30 au); it is interpreted as a disk viewed almost edge-on. Optically thick thermal emission from ∼500 K dust is the most plausible source of the continuum, even at frequencies as low as 43 GHz; the disk mass is most likely in the range 0.02–0.2 M{sub ⊙}. A rich spectrum of molecular lines is detected, mostly from sulfur- and silicon-rich molecules like SO, SO{sub 2}, and SiS, but also including vibrationally excited CO and several unidentified transitions. Lines with upper energy levels E{sub U}>500 K appear in emission and are symmetric about the source’s LSR velocity of 5 km s{sup −1}, while lines with E{sub U}<500 K appear as blueshifted absorption features against the continuum, indicating that they originate in outflowing gas. The emission lines exhibit a velocity gradient along the major axis of the disk that is consistent with rotation around a 5–7 M{sub ⊙} central object. The relatively low mass of SrcI and the existence of a 100 au disk around it are difficult to reconcile with the model in which SrcI and the nearby Becklin–Neugebauer Object were ejected from a multiple system 500 years ago.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Observation of Z b ( 10610 ) and Z b ( 10650 ) Decaying to B Mesons

We detail the analysis of the three-body e + e - → B B ¯ π ± , B B ¯ * π ± , and B * B ¯ * π ± processes, including the first observations of the Z b ± ( 10 610 ) → [ B B ¯ * + c . c . ] ± and Z b ± ( 10 650 ) → [ B * B ¯ * ] ± transitions that are found to dominate the corresponding final states. We measure Born cross sections for the three-body production of σ ( e + e - → [ B B ¯ * + c . c . ] ± π ∓ ) = [ 17.4 ± 1.6 ( stat ) ± 1.9 ( syst ) ] pb and σ ( e + e - → [ B * B ¯ * ] ± π ∓ ) = [ 8.75 ± 1.15 ( stat ) ± 1.04 ( syst ) ] pb and set a 90% C.L. upper limit of σ ( e + e - → [ B B ¯ ] ± π ∓ ) < 2.9 pb . The results are based on a 121.4 fb - 1 data sample collected with the Belle detector at a center-of-mass energy near the Υ ( 10 860 ) peak.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Quasireal Compton scattering measurement and e* scattering with DELCO at PEP

We report on a measurement of the elastic scattering of quasi-real photons generated by one beam with the particles of the other in e + e - interactions at $\sqrt{s}$ = 29 GeV performed using the DELCO detector at PEP. The events are characterized by coplanar and anti-tagged ey pairs with large visible energy where the charge of the electron is correlated with the acolinearity angle. We also use our result to search for the on-shell production of a hypothetical excited electron e*. We find that the data agree well with the predictions for the QED Compton process, and set upper limits on the e*e&gamma; coupling parameter λ to be below 10 -2 (95% C.L.) in the range 15 ≲ M e* 27 GeV.

Bonneaud, G.↗
DOE OSTI2024

Search for the production of deuterons and antideuterons in e + e − annihilation at center-of-mass energies between 4.13 and 4.70 GeV

Using a data sample of e + e − collision data corresponding to an integrated luminosity of 19 fb − 1 collected with the BESIII detector at the BEPCII collider, we search for the production of deuterons and antideuterons via e + e − → p p π − d ¯ + c . c . for the first time at center-of-mass energies between 4.13 and 4.70 GeV. No significant signal is observed and the upper limit of the e + e − → p p π − d ¯ + c . c . cross section is determined to be from 9.0 to 145 fb depending on the center-of-mass energy at the 90% confidence level. Published by the American Physical Society 2024

Ablikim, M.↗