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70 个结果
  • 简介:AnewlayeredCu-basedoxychalcogenideBa3Fe2O5Cu2S2hasbeensynthesizedanditsmagneticandelectronicpropertieswererevealed.Ba3Fe2O5Cu2S2isbuiltupbyalternativelystacking[Cu2S2]2-layersandironperovskiteoxide[(FeO2)(BaO)(FeO2)]2-layersalongthecaxisthatareseparatedbybariumionswithFe3+fivefoldcoordinatedbyasquare-pyramidalarrangementofoxygen.Fromthebondvalencearguments,weinferredthatinlayeredCuCh-based(Ch=S,Se,Te)compoundsthe+3cationinperovskiteoxidesheetprefersasquarepyramidalsite,whilethelowervalencecationprefersthesquareplanarsites.Thestudiesonsusceptibility,transport,andopticalreflectivityindicatethatBa3Fe2O5Cu2S2isanantiferromagneticsemiconductorwithaNe′eltemperatureof121Kandanopticalbandgapof1.03eV.Themeasurementofheatcapacityfrom10Ktoroomtemperatureshowsnoanomalyat121K.TheDebyetemperatureisdeterminedtobe113K.TheoreticalcalculationsindicatethattheconductionbandminimumispredominantlycontributedbyO2pand3dstatesofFeionsthatantiferromagneticallyarrangedinFeO2layers.TheFe3dstatesarelocatedatlowerenergyandresultinanarrowbandgapincomparisonwiththatoftheisostructuralSr3Sc2O5Cu2S2.

  • 标签: 钙钛矿型氧化物 铁磁半导体 光学带隙 德拜温度 电子性质 阳离子
  • 简介:Inthisarticle,theSm-dopingsinglecrystalsCa1-xSmxFe2As2(x=00.2)werepreparedbytheCaAsfluxmethod,andfollowedbyarapidquenchingtreatmentafterthehightemperaturegrowth.Thesampleswerecharacterizedbystructural,resistive,andmagneticmeasurements.ThesuccessfulSm-substitutionwasrevealedbythereductionofthelatticeparameterc,duetothesmallerionicradiusofSm3+thanCa2+.SuperconductivitywasobservedinallsampleswithonsetTcvaryingfrom27Kto44KuponSm-doping.ThecoexistenceofacollapsedphasetransitionandthesuperconductingtransitionwasfoundforthelowerSm-dopingsamples.ZeroresistivityandsubstantialsuperconductingvolumefractiononlyhappeninhigherSm-dopingcrystalswiththenominalx>0.10.Thedopingdependencesofthec-axislengthandonsetTcweresummarized.Thehigh-TcobservedinthesequenchedcrystalsmaybeattributedtosimultaneoustuningofelectroncarriersdopingandstraineffectcausedbylatticereductionofSm-substitution.

  • 标签: 掺杂晶体 超导电性 SM 单晶 晶格参数 淬火温度
  • 简介:Takingadvantageofthelargeγ-detectorarrayGammasphereandtherecoilmassseparatorFMA,highspinstatesin117Bawereinvestigatedthroughtherecoil-β-delayedprotondecaytaggingtechniqueviatheheavy-ioninducedfusion-evaporationreaction64Zn(58Ni,2p3n)117Ba,atabeamenergyof305MeV.Promptγraysbelongingto117Bahavebeenidentifiedfurthermore,arotationalbandhasbeenidentifiedforthefirsttimeandpresentedasbandAinFig.1.

  • 标签: ADVANTAGE FMA VIA HAS
  • 简介:Anewmethodforfabricatingorderedporoussiliconisreported.Atwo-dimensionalsilicananospherearrayisusedasatemplatewithahydrofluoricacid-hydrogenperoxidesolutionforetchingthenanospheres.Theinitialdiameteranddistributionoftheholesintheresultingporoussiliconlayeraredeterminedbythesizeanddistributionofthesilicananospheres.Thecorrosiontimecanbeusedtocontrolthedepthsoftheholes.ItisfoundthatthepresenceofaSiO_2layer,formedbytheoxidationoftheroughinternalsurfaceofthehole,istheprimaryreasonallowingthecorrosiontoproceed.Ultravioletreflectionandthermalconductivitymeasurementsshowthatthediameteranddistributionoftheholeshaveagreatinfluenceonpropertiesoftheporoussilicon.

  • 标签: 二氧化硅层 制备方法 多孔硅 有序 模板 二维
  • 简介:我们揭示并且解释thermopowerS/T的可伸缩的行为展出了由典型重费米子(HF)金属YbRh2在在温度T的磁场B的申请下面的Si2。我们证明一样的可伸缩被不同HF混合物例如表明?-YbAlB4和强烈相关的分层的钴氧化物[BiBa0.66K0.36O2]CoO2。用YbRh2是的Si2一个例子,,我们证明S/T的可伸缩的行为在antiferromagnetic阶段转变被违背剩余抵抗力0和状态的密度,N,经验在阶段转变跳,引起thermopower做二跳并且改变它的符号。我们的说明基于深刻地影响0和N的单个粒子的光谱变平。描绘S/T行为的主要特征,我们构造TBYbRh2Si2。我们为HF混合物的计算S/T在对试验性的事实的好同意并且支持我们的观察。

  • 标签: 标度行为 重费米子 热电势 金属 原型 铁磁相变
  • 简介:Twofamiliesofcatalysts,basedonPdnanoparticlessupportedonceramicasymmetrictubularaluminamembranes,arestudiesinthedirectsynthesisofH_2O_2.TheyarepreparedbydepositingPdintwoways:(i)reductionwithN_2H_4inanultrasonicbathand(ii)byimpregnation-deposition.Thefirstpreparationleadstolargerparticles,withaveragesizeofaround11nm,whilethesecondpreparationleadstosmallerparticles,withaveragesizearound4nm.Thecatalyticmembranesweretestedasprepared,afterthermaltreatmentinairandafterfurtherpre-reductionwithH_2inmild(100℃)conditions.SampleswerecharacterizedbyTEM,CO-chemisorptionmonitoredbyDRIFTSmethodandTPR,whilecatalytictestshavebeenperformedinasemi-batchrecirculationmembranereactor.Experimentalcatalyticresultswereanalysedusingtwokineticsmodelstoderivethereactionconstantsfortheparallelandconsecutivereactionsofthekineticnetwork.SmallerparticlesofPdshowlowerselectivityduetothehigherrateofparallelcombustion,evenifthebetterdispersionofPdandthushighermetalsurfaceareainthesampleleadtoaproductivityinH_2O_2similarorevenhigherthanthesamplewiththelargerPdparticles.IndependentlyonthepresenceofsmallerorlargerPdnanoparticles,anoxidationtreatmentleadstoasignificantenhancementintheproductivity,althoughthecatalystprogressivelyreducesduringthecatalyticprocess.Theinhibitionoftheparallelcombustionreaction(towater)inducedfromthecalcinationtreatmentremainsafterthein-situreductionoftheoxidizedPdspeciesformedduringthepre-treatment.Thisislikelyduetotheeliminationofdefectsiteswhichdissociativelyactivateoxygen,andtentativelyattributedtoPdsitesabletogivethree-andfour-foldcoordinationofCO.

  • 标签: 钯纳米粒子 过氧化氢 直接合成 预处理 TEM样品 动力学模型
  • 简介:Nuclearmassisoneofthefundamentalquantityofatomicnucleus.Thetotalbindingenergyofanucleusderivedfromtherelatedmassvaluesreflectsalltheinteractionsamongtheconstitutingnucleons.Massesofshort-livedA=2Z+3nucleiof112SnprojectilefragmentshavebeenmeasuredattheexperimentalcoolerstorageringCSRe,employingtheIsochronousmassspectrometry(IMS).TheexperimentwasconductedattheHeavyIonResearchFacilityinLanzhouatthebeginningof2016.Theprimarybeamof112Sn35+wasaccumulatedinthesynchrotronCSRmandacceleratedto467.91MeV/u.Secondarybeamwereproducedbyimpingingthehighintensity112Sn35+beamontoa10mmberylliumtargetwhichwaslocatedattheentranceoftheradioactivebeamlineRIBLL2.Theprojectilefragmentsof112Snemergedfromthetargetwerethentransmitted,separatedinflightthroughRIBLL2andfinallyinjectedintoCSRe.

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  • 简介:Lifetimemeasurementsoflow-lyingexcitedstatesin^87Zrhavebeenperformedviaβ-γcoincidences.The127MeV^32SbeamwasdeliveredfromtheSector-FocusingCyclotron(SFC)oftheHeavyIonResearchFacilityinLanzhou(HIRFL).Theparentnuclei^87Nbwereproducedbythereaction58Ni(32S,2p1n),atabeamenergy127MeVthrougha8umAldegrader.A200ug/cm^2layerof58Nievaporatedontoa200ug/cm^2thickcarbonfoilwasemployedasthetarget.Afterevaporationresidueswereseparatedfromtheprojectilebeamsbythegas-filledrecoilseparatorSHANS[1],thenucleiofinterest87Zrcanbeobtainedwithahigherpurityandthenwereimplantedintoa300umsilicondetector.

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  • 简介:选用aug-cc-pVTZ及aug-cc-pVQZ基组对不同H2-H2位形进行了量子化学计算,外推出了氢分子间各向异性ab-initio作用势。依据实验数据确定出氢分子相互作用的5-体模型,在全局最优算法基础上拟合出了包含电四极矩项、多体极化作用项及三体关联项等在内的氢分子间各向异性作用势。结果验证了拟合势与ab-initio势能曲线几乎重合,两者偏差落在(-1.35K,1.29K)范围内;得出的氢分子第二维里系数与实验结果一致。

  • 标签: 氢分子 各向异性作用势 从头计算
  • 简介:WehavestudiedtheangularmagnetoresistanceofironpnictidesBaFe2-xNixAs2,whichshowsclear180degreeperiodicityasfittedbyacosinefunction.Inthex=0.065sample,thephaseofthetwo-foldsymmetrychanges90degreesabovethetetragonal-to-orthorhombicstructuraltransitiontemperatureTs.Sincethephaseatlowtemperatureisassociatedwiththerotationoforthorhombicdomainsbymagneticfield,weshowthatevenvacuumgreasecanpushthepresenceoforthorhombicdomainsattemperaturesmuchhigherthanTs.Ourresultssuggestthatresidualstressmayhavesignificanteffectsinstudyingthenematicordersanditsfluctuationsinironpnictides.

  • 标签: 残余应力 磁电阻 转变温度 函数拟合 斜方晶系 周期性
  • 简介:TheapplicationofLanthanumBromide(LaBr3)detectorsprovidesauniqueopportunitytomeasurelifetimeofexcitedstatesinpicosecond-nanosecondregion.Reducingthebackgroundisofcriticalimportancetogetpreciseresults.Forsomeexcitedstatesfeedingfromisomerswithlifetimelongerthan1μs,itcanbeachievedbytheSpectrometerforHeavyAtomandNuclearStructure(SHANS)[1].143Eunucleiwerepopulatedviathe123Sb(24Mg,4n)fusion-evaporationreaction.Mostoftheevaporationresiduesatgroundstateorlong-livedisomersweretransferredtodetectionterminalafteraflightofabout1.4μsinSHANS.Inthecaseof143Eu,threetransitionshavebeenobserved(Fig.1).

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  • 简介:ThecapacitytocaptureCO2wasdeterminedinseveralstoichiometriccompositionsintheLi2O–Bi2O3system.Thecompounds(Li7BiO6,Li5BiO5,Li3BiO4andLiBiO2phases)weresynthesizedviasolid-statereactionandcharacterizedbyX-raydiffraction,scanningelectronmicroscopyandN2adsorptiontechniques.Thesampleswereheat-treatedattemperaturesfrom40to750°CundertheCO2atmospheretoevaluatethecarbonateformation,whichisindicativeofthecapacityofCO2capture.Moreover,Li7BiO6showsanexcellentCO2capturecapacityof7.1mmol/g,whichisconsiderablyhigherthanthoseofotherpreviouslyreportedceramics.Li7BiO6isabletoreactwithCO2from240°Ctoapproximately660°CshowingahighkineticreactionevenatCO2partialpressurevaluesaslowas0.05.

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  • 简介:DigitaldecayspectroscopyofactinideisotopesatthegasfilledseparatorSHANSAlloverthechartofnuclides,theregiontothe“north-east”of208Pb,withZ≥84andN=128~130,hoststheshortest-livedαradioactivities,withhalf-livesintherangeofnanosecondstomicroseconds.Synthesisanddetectionofneutron-deficientisotopesabovethoriuminthisregionarechallengingduetotheirlowproductioncrosssectionsandshorthalf-lives.

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  • 简介:Thescientificprogramofthegroupcoversbigbangnucleosynthesis,hydrostaticburninginstarsandexplosivenucleosynthesisinsupernova.Byconsideringnon-equilibriumstatistics,wesuggestapossiblewaytosolvetheLiprobleminbigbangnucleosynthesis.The13C(α,n)16Oisthemajorneutronsourceforthes-processhappeninginAGBstars.The19F(p,α)16Oisrelevanttotheproductionoffluorine.WearedevelopingexperimentalplatformstostudytheimportantreactionforthefirsttimedirectlyattheirstellarenergiesinJinpingUndergroundLaboratory.The59Festellardecayrateisimportantfortheproductionof60Fe,animportantisotopewhosegammarayhasbeenobservedbysatellites.WedetermineitsstellardecayrateforthefirsttimeusingexperimentalB(GT)strength.Thenewratereducesthediscrepancyofthe60Feyieldsbetweenthemodelpredictionsandtheobservations.Theundergroundexperimentisexpectedtobeginin2018.

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  • 简介:IntheBigBangtheory,primordialnucleosynthesiswasfinishedduringfirsthalfhouroftheuniverse’sexistence.Thisprocessyieldedthemainlightelementsincludinghydrogen,deuterium,heliumandlithium.Thetheoreticalpredictionsmatchverywelltheobserveddeuteriumandheliumabundance,butthe7Liabundanceisoverpredictedbyafactorathree[1].Thisinconsistencyiscalled“cosmologicallithiumproblem”.Inthepastdecade,manyattemptstosolvethisproblemusingconventionalastrophysicsandnuclearphysicsfailed.Recently,weproposedanewsolutiontolithiumproblembyintroducingnon-extensivestatisticsintoBigBangnucleosynthesis[2].

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  • 简介:JUNA(JinpingUndergroundlaboratoryforNuclearAstrophysics)isplaningtomeasurethe13C(α,n)16OandsomeotherimportantreactionsatorclosetostellarenergiesusingintenseheliumbeamoutofanECRdrivenacceleratorinJinpingUndergroundlaboratory[1].Deuteriumimpurityinionsourcewillproducessignificantamountofneutrons,limitingthebackgroundlevel.Tocontrolthedeteriumimpurity,wehavedevelopedamethodtomeasurethedeuteriumimpuritywithinHeliumbeamusingthed(d,p)treaction.

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  • 简介:Asafundamentalpropertyofnuclei,atomicmassesarewidelyusedinmanydomainsofscienceandengineering.Areliableatomicmasstablederivedfromtheexperimentaldata,wheretheatomicmassesandtherelevantexperi-mentalinformationcanbefoundconveniently,isinhighdemandbytheresearchcommunity.Tomeetthedemands,theAtomicMassEvaluation(AME)wasinitiatedin1950'sandaseriesofAMEmasstableshavebeenpublishedeversince.CurrentlytheAMEservestheresearchcommunitybyprovidingthemostreliableandcomprehensiveinformationrelatedtotheatomicmasses.ThenewatomicmassevaluationAME2016waspublishedintheMarchissueofChinesePhysicsCastwocom-plementarypapers[1;2].

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  • 简介:134Csabranchingpointins-processpathwhichisshowninFig.1.Thebranchingratioisdefinedasfβ=λβ/(λβ+λn).Itcouldbededucedfromtheabundanceof134Baand136Basince136Bagoesthroughbothdecayandneutroncaptureof134Cswhile134Baonlyexperiencesdecaychannel[1].Duetoboth134Baand134Baarepures-processnuclei,thisbranchingpointisagoodapproachtodeterminethes-processparameters.Withtemperaturedependentβ-decayrateof134Cs,thetemperatureofs-processcouldbededuced.

  • 标签: PATH GOES IS BE