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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The seasonal variations of ozone and temperature in the middle and the upper stratosphere

The seasonal variations in ozone and temperature inferred from the Nimbus-4 BUV (Backscatter Ultraviolet Spectrometer) and the SCR (Selective Chopper Radiometer) experiments are compared with predictions based on a simplified radiative photochemical model. It is shown that the observations, in agreement with the model calculations, show a systematic phase shift from a summer maximum at 10 mb to a winter maximum at 1 mb with equinoctial maxima at intermediate heights. In contrast, the temperature between these pressure levels shows no appreciable phase shift and the summer maximum prevails at all heights. The observed phase differences in ozone and temperature are shown to be a manifestation of the radiative feedback on the photochemistry of the upper stratosphere.

Chandra, S.↗
DOE OSTI2021

Exploring the Spatial Control of Topotactic Phase Transitions Using Vertically Oriented Epitaxial Interfaces

Engineering oxygen vacancy formation and distribution is a powerful route for controlling the oxygen sublattice evolution that affects diverse functional behavior. The controlling of the oxygen vacancy formation process is particularly important for inducing topotactic phase transitions that occur by transformation of the oxygen sublattice. Here we demonstrate an epitaxial nanocomposite approach for exploring the spatial control of topotactic phase transition from a pristine perovskite phase to an oxygen vacancy-ordered brownmillerite (BM) phase in a model oxide La 0.7 Sr 0.3 MnO 3 (LSMO). Incorporating a minority phase NiO in LSMO films creates ultrahigh density of vertically aligned epitaxial interfaces that strongly influence the oxygen vacancy formation and distribution in LSMO. Combined structural characterizations reveal strong interactions between NiO and LSMO across the epitaxial interfaces leading to a topotactic phase transition in LSMO accompanied by significant morphology evolution in NiO. Using the NiO nominal ratio as a single control parameter, we obtain intermediate topotactic nanostructures with distinct distribution of the transformed LSMO-BM phase, which enables systematic tuning of magnetic and electrical transport properties. The use of self-assembled heterostructure interfaces by the epitaxial nanocomposite platform enables more versatile design of topotactic phase structures and correlated functionalities that are sensitive to oxygen vacancies.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Laser Welding-Brazing of Immiscible AZ31B Mg and Ti-6Al-4V Alloys Using an Electrodeposited Cu Interlayer

Metallurgical bonding between immiscible system AZ31B magnesium (Mg) and Ti-6Al-4V titanium (Ti) was achieved by adding Cu interlayer using laser welding-brazing process. Effect of the laser power on microstructure evolution and mechanical properties of Mg/Cu-coated Ti joints was studied. Visually acceptable joints were obtained at the range of 1300 to 1500 W. The brazed interface was divided into three parts due to temperature gradient: direct irradiation zone, intermediate zone and seam head zone. Ti{sub 3}Al phase was produced along the interface at the direct irradiation zone. Ti-Al reaction layer grew slightly with the increase in laser power. A small amount of Ti{sub 2}(Cu,Al) interfacial compounds formed at the intermediate zone and the (α-Mg + Mg{sub 2}Cu) eutectic structure dispersed in the fusion zone instead of gathering when increasing the laser power at this zone. At the seam head zone, Mg-Cu eutectic structure was produced in large quantities under all cases. Joint strength first increased and then decreased with the variation of the laser power. The maximum fracture load of Mg/Cu-coated Ti joint reached 2314 N at the laser power of 1300 W, representing 85.7% joint efficiency when compared with Mg base metal. All specimens fractured at the interface. The feature of fracture surface at the laser power of 1100 W was characterized by overall smooth surface. Obvious tear ridge and Ti{sub 3}Al particles were observed at the fracture surface with increase in laser power. It suggested atomic diffusion was accelerated with more heat input giving rise to the enhanced interfacial reaction and metallurgical bonding in direct irradiation zone, which determined the mechanical properties of the joint.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Discretized evolution of solitons in the achiral stripe phase of a Fe/Gd thin film

Understanding magnetic phase transitions from stripe to skyrmion textures provide fundamental scientific insights into the details of the intermediate topologies through which the system evolves. The solitonic nature of spin texture in both stripe and skyrmion phases has been observed in materials with Dzyaloshinskii-Moriya interaction. In this study we show that the field evolution in a dipolar interaction mediated Fe/Gd multilayer that exhibits achiral stripe textures behaves similar to a finite-sized chiral soliton lattice. As a function of magnetic field, the stripes exhibit discrete jumps in periodicity indicative of intermediate topologies as the stripes get wound into skyrmions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Isomer-Selective Detection of Keto-Hydroperoxides in the Low-Temperature Oxidation of Tetrahydrofuran

Keto-hydroperoxides (KHPs) are reactive, partially oxidized intermediates that play a central role in chain-branching reactions during the gas-phase low-temperature oxidation of hydrocarbons and oxygenated species. Although multiple isomeric forms of the KHP intermediate are possible in complex oxidation environments when multiple reactant radicals exist that contain nonequivalent O 2 addition sites, isomer-resolved data of KHPs have not been reported. In this work, we provide partially isomer-resolved detection and quantification of the KHPs that form during the low-temperature oxidation of tetrahydrofuran (THF, cycl. -O–CH 2 CH 2 CH 2 CH 2 –). We describe how these short-lived KHPs were detected, identified, and quantified using integrated experimental and theoretical approaches. The experimental approaches were based on direct molecular-beam sampling from a jet-stirred reactor operated at near-atmospheric pressure and at temperatures between 500 and 700 K, followed by mass spectrometry with single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation, and the identification of fragmentation patterns. The interpretation of the experiments was guided by theoretical calculations of ionization thresholds, fragment appearance energies, and photoionization cross sections. On the basis of the experimentally observed and theoretically calculated ionization and fragment appearance energies, KHP isomers could be distinguished as originating from H-abstraction reactions from either the α-C adjacent to the O atom or the β-C atoms. Temperature-dependent concentration profiles of the partially resolved isomeric KHP intermediates were determined in the range of 500–700 K, and the results indicate that the observed KHP isomers are formed overwhelmingly (~99%) from the α-C THF radical. Furthermore, the comparisons of the partially isomer-resolved quantification of the KHPs to up-to-date kinetic modeling results reveal new opportunities for the development of a next-generation THF oxidation mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

A 100 Mbps resonant cavity phase modulator for coherent optical communications

A resonant cavity electro-optic phase modulator has been designed and implemented to operate at a data rate of 100 Mbps. The modulator consists of an electro-optic crystal located in a highly resonant cavity. The cavity is electro-optically tuned on and off resonance, and the phase dispersion near the cavity resonance provides the output phase modulation. The performance of the modulator was measured by first heterodyne detecting the signal to an intermediate frequency and then measuring the spectral characteristics using an RF spectrum analyzer. The measured phase shift is shown to be in good agreement with the theoretical predictions.

Chen, Chien-Chung↗
DOE OSTI2020

Direct Observation of Alternating Octahedral and Prismatic Sodium Layers in O3-Type Transition Metal Oxides

The oxygen stacking of O3-type layered sodium transition metal oxides (O3-NaTMO 2 ) changes dynamically upon topotactic Na extraction and reinsertion. While the phase transition from octahedral to prismatic Na coordination that occurs at intermediate desodiation by transition metal slab gliding is well understood, the structural evolution at high desodiation, crucial to achieve high reversible capacity, remains mostly uncharted. In this work, the phase transitions of O3-type layered NaTMO 2 at high voltage are investigated by combining experimental and computational approaches. An OP2-type phase that consists of alternating octahedral and prismatic Na layers is directly observed by in situ X-ray diffraction and high-resolution scanning transmission electron microscopy. The origin of this peculiar phase is explained by atomic interactions involving Jahn–Teller active Fe 4+ and distortion tolerant Ti 4+ that stabilize the local Na environment. Finally, the path-dependent desodiation and resodiation pathways are also rationalized in this material through the different kinetics of the prismatic and octahedral layers, presenting a comprehensive picture about the structural stability of the layered materials upon Na intercalation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Reactions of Studtite UO 4 ·4H 2 O in Alkali Hydroxides: Isolation of Single-Crystal Uranate Phases under Mild Hydrothermal Conditions

Uranyl peroxide complexes, particularly studtite (UO 4 ·4H 2 O), are important phases within the nuclear fuel cycle, forming through radiolysis-induced reactions on the surfaces of spent fuel and in waste environments. Studtite has been identified in Hanford’s irradiated fuel storage basins, Chornobyl’s corium lavas, and is anticipated on Fukushima’s fuel debris. While its formation and stability have been extensively studied, the reactivity of UO 4 ·4H 2 O in highly alkaline environments such as those encountered in high-level nuclear waste remains underexplored. These environments contain molar concentrations of [OH - ] and present a chemically dynamic and reactive environment where actinide behavior is not well understood. Reported here are investigations of uranium reactions in concentrated alkali hydroxides under mild hydrothermal conditions (<200 °C) that have resulted in the isolation of the alkali metal uranates Li 2 UO 4 , α-Na 2 UO 4 , γ-Na 2 U 2 O 7 , and K 2 U 2 O 7 . In contrast to conventional solid-state methods (>800 °C) that typically yield polycrystalline powders, our approach enables the isolation of these uranates as single crystals, allowing us to provide single-crystal structure solutions of certain uranates for the first time. Our findings match the results of high-level waste tank sampling, confirming that sodium diuranate (Na 2 U 2 O 7 ) is the most persistent uranium phase, potentially forming through reactions of uranyl peroxide intermediates with NaOH under radiolytic and highly alkaline conditions.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

Structure-electrochemical evolution of a Mn-rich P2 Na 2/3 Fe 0.2 Mn 0.8 O 2 Na-ion battery cathode

The structural evolution of electrode materials directly influences the performance of sodium-ion batteries. In this work, in situ synchrotron X-ray diffraction is used to investigate the evolution of the crystal structure of a Mn-rich P2-phase Na 2/3 Fe 0.2 Mn 0.8 O 2 cathode. A single-phase reaction takes place for the majority of the discharge–charge cycle at ~C/10, with only a short, subtle hexagonal P2 to hexagonal P2 two-phase region early in the first charge. Thus, a higher fraction of Mn compared to previous studies is demonstrated to stabilize the P2 structure at high and low potentials, with neither “Z”/OP4 phases in the charged state nor significant quantities of the P'2 phase in the discharged state between 1.5 and 4.2 V. Notably, sodium ions inserted during discharge are located on both available crystallographic sites, albeit with a preference for the site sharing edges with the MO 6 octahedral unit. The composition Na ~0.70 Fe 0.2 Mn 0.8 O 2 prompts a reversible single-phase sodium redistribution between the two sites. Sodium ions vacate the site sharing faces (Naf), favoring the site sharing edges (Nae) to give a Nae/Naf site occupation of 4:1 in the discharged state. This site preference could be an intermediate state prior to the formation of the P'2 phase. Furthermore, this work shows how the Mn-rich Na 2/3 Fe 0.2 Mn 0.8 O 2 composition and its sodium-ion distribution can minimize phase transitions during battery function, especially in the discharged state.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Multiscale Electrochemomechanics Interaction and Degradation Analytics of Sn Electrodes for Sodium-Ion Batteries

Sodium-ion batteries have emerged as a strong contender among the beyond lithium-ion chemistries due to elemental abundance and the low cost of sodium. Tin (Sn) is a promising alloying electrode with high capacity, redox reversibility, and earth abundance. Tin electrodes, however, undergo a series of intermediate reactions exhibiting multiple voltage plateaus upon sodiation/desodiation. Phase transformations related to incomplete sodiation in tin during cycling, in the presence of a frail solid electrolyte interphase layer, can quickly weaken the structural stability. The structural dynamics and reactivity of the electrode/electrolyte interface, being further dependent on the size and morphology of the active material particle in the presence of different electrolytes, dictate the electrode degradation and survivability during cycling. Here, we paint a comprehensive picture of the underpinnings of the electrochemical and mechanics coupling and electrode/electrolyte interfacial interactions in alloying Sn electrodes. We elicit the fundamental role of electrode/electrolyte complexations in the Sn electrode structure-property-performance relationship based on multimodal analytics, including electrochemical, microscopy, and tomography analyses.

25 ENERGY STORAGE↗
DOE OSTI2025

The Role of Interfaces and Charge for Chemical Reactivity in Microdroplets

A wide variety of reactions are reported to be dramatically accelerated in aqueous microdroplets, making them a promising platform for environmentally clean chemical synthesis. However, to fully utilize the microdroplets for accelerating chemical reactions requires a fundamental understanding of how microdroplet chemistry differs from that of a homogeneous phase. Here, in this work, we provide our perspective on recent progress to this end, both experimentally and theoretically. We begin by reviewing the many ways in which microdroplets can be prepared, creating water/hydrophobic interfaces that have been frequently implicated in microdroplet reactivity due to preferential surface adsorption of solutes, persistent electric fields, and their acidity or basicity. These features of the interface interplay with specific mechanisms proposed for microdroplet reactivity, including partial solvation, possible gas phase channels, and the presence of highly reactive intermediates. We especially highlight the role of droplet charge and associated electric fields, which appears to be key to understanding how certain reactions, like the formation of hydrogen peroxide and reduced transition metal complexes, are thermodynamically possible in microdroplets. Lastly, we emphasize opportunities for theoretical advances and suggest experiments that would greatly enhance our understanding of this fascinating subject.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Non-equilibrium reaction and relaxation dynamics in a strongly interacting explicit solvent: F + CD{sub 3}CN treated with a parallel multi-state EVB model

We describe a parallelized linear-scaling computational framework developed to implement arbitrarily large multi-state empirical valence bond (MS-EVB) calculations within CHARMM and TINKER. Forces are obtained using the Hellmann-Feynman relationship, giving continuous gradients, and good energy conservation. Utilizing multi-dimensional Gaussian coupling elements fit to explicitly correlated coupled cluster theory, we built a 64-state MS-EVB model designed to study the F + CD{sub 3}CN → DF + CD{sub 2}CN reaction in CD{sub 3}CN solvent (recently reported in Dunning et al. [Science 347(6221), 530 (2015)]). This approach allows us to build a reactive potential energy surface whose balanced accuracy and efficiency considerably surpass what we could achieve otherwise. We ran molecular dynamics simulations to examine a range of observables which follow in the wake of the reactive event: energy deposition in the nascent reaction products, vibrational relaxation rates of excited DF in CD{sub 3}CN solvent, equilibrium power spectra of DF in CD{sub 3}CN, and time dependent spectral shifts associated with relaxation of the nascent DF. Many of our results are in good agreement with time-resolved experimental observations, providing evidence for the accuracy of our MS-EVB framework in treating both the solute and solute/solvent interactions. The simulations provide additional insight into the dynamics at sub-picosecond time scales that are difficult to resolve experimentally. In particular, the simulations show that (immediately following deuterium abstraction) the nascent DF finds itself in a non-equilibrium regime in two different respects: (1) it is highly vibrationally excited, with ∼23 kcal mol{sup −1} localized in the stretch and (2) its post-reaction solvation environment, in which it is not yet hydrogen-bonded to CD{sub 3}CN solvent molecules, is intermediate between the non-interacting gas-phase limit and the solution-phase equilibrium limit. Vibrational relaxation of the nascent DF results in a spectral blue shift, while relaxation of the post-reaction solvation environment results in a red shift. These two competing effects mean that the post-reaction relaxation profile is distinct from what is observed when Franck-Condon vibrational excitation of DF occurs within a microsolvation environment initially at equilibrium. Our conclusions, along with the theoretical and parallel software framework presented in this paper, should be more broadly applicable to a range of complex reactive systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom

The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl{sub 2}F–CClF{sub 2}, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl{sub 2}F–CCl{sub 2}F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Complex magnetic properties in the mixed 4 f - 5 d double perovskite iridates X 2 ZnIrO 6 ( X = Nd , Sm , Eu , Gd )

Here in this paper, we report on the synthesis and magnetic properties of a series of double perovskites Ln 2 ZnIrO 6 with Ln = Nd, Sm, Eu, Gd. These compounds present examples of the rare case of double perovskites (general formula A 2 BB'O6) with a magnetic 4ƒ-ion on the A site in combination with the strongly spin-orbit coupled 5d transition-metal ion Ir 4+ on the B sublattice. We discuss the impact of different rare earths on the macroscopic magnetic properties. Gd 2 ZnIrO 6 and Eu 2 ZnIrO 6 show ferrimagnetic or canted antiferromagnetic order below T N = 23 and 12 K, respectively. Sm 2 ZnIrO 6 orders antiferromagnetically at T N = 13 K. Nd 2 ZnIrO 6 exhibits more complex magnetic properties with a strong field dependence ranging from a two-step spin reorientation at μ 0 H = 0.01 T to an antiferromagnetic ground state at intermediate external fields to a spin-flop phase for 0H ≥ 4 T. This unique behavior suggests an interesting interplay between Nd 3+ and Ir 4+ . To further shed light on the relevant magnetic interaction, the zero-field magnetic ground state of Nd 2 ZnIrO 6 is examined via neutron powder diffraction. In general, the magnetic properties of Ln 2 ZnIrO 6 hint towards a substantial contribution of the rare-earth ions and a significant correlation between 5d and 4ƒ magnetism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Local and long-range atomic/magnetic structure of non-stoichiometric spinel iron oxide nanocrystallites

Spinel iron oxide nanoparticles of different mean sizes in the range 10–25 nm have been prepared by surfactant-free up-scalable near- and super-critical hydrothermal synthesis pathways and characterized using a wide range of advanced structural characterization methods to provide a highly detailed structural description. The atomic structure is examined by combined Rietveld analysis of synchrotron powder X-ray diffraction (PXRD) data and time-of-flight neutron powder-diffraction (NPD) data. The local atomic ordering is further analysed by pair distribution function (PDF) analysis of both X-ray and neutron total-scattering data. It is observed that a non-stoichiometric structural model based on a tetragonal γ-Fe 2 O 3 phase with vacancy ordering in the structure (space group P 4 3 2 1 2) yields the best fit to the PXRD and total-scattering data. Detailed peak-profile analysis reveals a shorter coherence length for the superstructure, which may be attributed to the vacancy-ordered domains being smaller than the size of the crystallites and/or the presence of anti-phase boundaries, faulting or other disorder effects. The intermediate stoichiometry between that of γ-Fe 2 O 3 and Fe 3 O 4 is confirmed by refinement of the Fe/O stoichiometry in the scattering data and quantitative analysis of Mössbauer spectra. The structural characterization is complemented by nano/micro-structural analysis using transmission electron microscopy (TEM), elemental mapping using scanning TEM, energy-dispersive X-ray spectroscopy and the measurement of macroscopic magnetic properties using vibrating sample magnetometry. Notably, no evidence is found of a Fe 3 O 4 /γ-Fe 2 O 3 core-shell nanostructure being present, which had previously been suggested for non-stoichiometric spinel iron oxide nanoparticles. Finally, the study is concluded using the magnetic PDF (mPDF) method to model the neutron total-scattering data and determine the local magnetic ordering and magnetic domain sizes in the iron oxide nanoparticles. The mPDF data analysis reveals ferrimagnetic collinear ordering of the spins in the structure and the magnetic domain sizes to be ∼60–70% of the total nanoparticle sizes. The present study is the first in which mPDF analysis has been applied to magnetic nanoparticles, establishing a successful precedent for future studies of magnetic nanoparticles using this technique.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Deposition and characterization of α-Fe 2 O 3 /Pd thin films for neutron reflectometry studies

Here, we report deposition of hematite/Pd thin films on silicon wafers via radio frequency (RF) magnetron sputtering and subsequent characterization for future in situ neutron reflectometry studies. Following deposition, the hematite/Pd thin films were characterized as prepared and after annealing in air for 2h at 400, 500, and 600 °C, respectively. Raman spectroscopy, grazing incidence x-ray diffraction, and neutron reflectometry (NR) were used to characterize the structure and chemical compositions of the thin films. The results indicate that pure α-Fe 2 O 3 (hematite) films were produced, free from other iron oxide phases and impurities. NR data reveal that one intermediate layer between the Pd layer and the hematite layer was formed during sputtering deposition processes. The fitted scattering length density (SLD) of the as-deposited hematite layer is 70% of the theoretical SLD value, indicating that the grains are loosely packed in the RF-deposited hematite films. After annealing at elevated temperatures, the hematite films show increased SLD values but remain comparable to that of preannealed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

STELLAR MASS–GAS-PHASE METALLICITY RELATION AT 0.5 ≤ z ≤ 0.7: A POWER LAW WITH INCREASING SCATTER TOWARD THE LOW-MASS REGIME

We present the stellar mass (M{sub ∗})–gas-phase metallicity relation (MZR) and its scatter at intermediate redshifts (0.5⩽z⩽0.7) for 1381 field galaxies collected from deep spectroscopic surveys. The star formation rate (SFR) and color at a given M{sub ∗} of this magnitude-limited (R≲24 AB) sample are representative of normal star-forming galaxies. For masses below 10{sup 9} M{sub ⊙}, our sample of 237 galaxies is ∼10 times larger than those in previous studies beyond the local universe. This huge gain in sample size enables superior constraints on the MZR and its scatter in the low-mass regime. We find a power-law MZR at 10{sup 8} M{sub ⊙} < M{sub ∗} < 10{sup 11} M{sub ⊙}: 12+log(O/H)=(5.83±0.19) +(0.30±0.02)log(M{sub ∗}/M{sub ⊙}). At 10{sup 9} M{sub ⊙} < M{sub ∗} < 10{sup 10.5} M{sub ⊙}, our MZR shows agreement with others measured at similar redshifts in the literature. Our power-law slope is, however, shallower than the extrapolation of the MZRs of others to masses below 10{sup 9} M{sub ⊙}. The SFR dependence of the MZR in our sample is weaker than that found for local galaxies (known as the fundamental metallicity relation). Compared to a variety of theoretical models, the slope of our MZR for low-mass galaxies agrees well with predictions incorporating supernova energy-driven winds. Being robust against currently uncertain metallicity calibrations, the scatter of the MZR serves as a powerful diagnostic of the stochastic history of gas accretion, gas recycling, and star formation of low-mass galaxies. Our major result is that the scatter of our MZR increases as M{sub ∗} decreases. Our result implies that either the scatter of the baryonic accretion rate (σ{sub M-dot }) or the scatter of the M{sub ∗}–M{sub halo} relation (σ{sub SHMR}) increases as M{sub ∗} decreases. Moreover, our measure of scatter at z=0.7 appears consistent with that found for local galaxies. This lack of redshift evolution constrains models of galaxy evolution to have both σ{sub M-dot }and σ{sub SHMR} remain unchanged from z=0.7 to z = 0.

79 ASTRONOMY AND ASTROPHYSICS↗