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1©Solid-stateNMRService2001absoluteintensityAdisplayorplotmodeinwhichthesignalintensityisproportionaltotheconcentrationofthespeciesproducingit.acquisitiontimeTimeduringwhichsignalisrecorded(seefigure1).attenuationThecontrolappliedtovoltages(includingsignalfromthesample)withinthespectrometer.Highattenuationgiveslow-voltage,low-attenuationgiveshigh-voltage.B0Thestaticmagneticfield.Themagneticfluxdensityisexpressedintesla,T,oroften,asanequivalent1Hresonancefrequency(forexample,300MHzfora7Tmagnet).B1Magneticfieldassociatedwitharadio-frequency(r.f.)pulse.OftenexpressedasanequivalentvalueinkHz.bandshapeUsuallyusedwhenreferringtoacomplexlineshapeoragroupofoverlappinglines.Complexbandshapesoftenarisefromquadrupolarnuclei(seefigure2).centrebandThesignalattheisotropicchemicalshift.Itspositionisthesameatallspin-rates.channelTheindividualfrequenciesorfrequencybandsofaspectrometer.Forexample:H-channel(proton),C-channel(carbon)orbroad-band(orX)channel(usuallyanythingexceptH).chemicalshiftNumberusedforreportingthepositionofaline(νi)relativetoareferenceline(νref)inahigh-resolutionspectrum.Thechemicalshiftparameterisdenotedδandquotedinppm.coherencepathwayDescriptionofanexperimentthatallowstheexcitationofthespinstobefollowed.Usefulforexperimentswhereexcitationorselectionofsignalfromone-,two-ormultiple-quantumtransitionsisneeded.contacttimeTimeduringwhichtwomatchedradio-frequencyfieldsareappliedsimultaneouslyinaCPexperiment.CPCross-polarisation.Anyexperimentwhereenergy(magnetisation)istransferredfromthenucleiofoneelement(oftenH)tothoseofanother.dead-timeTimebetweenapulseandtheswitchonofthereceiver.Thespectrometercircuitryneedstimetosettleaftertransmittingthehighvoltageassociatedwithapulsebeforeitcandetecttheverylowvoltageassociatedwiththesignalfromthesample.Seefigure1.610×−=refrefiνννδTerminologyCommonlyUsedinNMRSpectroscopyFigure2.Bandshapefromasingle11Benvironment.Figure1.Signalisacquiredinthetimedomain.AcquisitiontimeFIDDeadtime©Solid-stateNMRService20012d.c.offsetConstant-valueoffsetoccurringintheFID(see“Problems”).Resultsinacentral(zero-frequency)“spike”artefactinthespectrumwhentransformed.deconvolutionMathematicalprocessusedtodeterminetheintensitiesofoverlappinglines.digitalresolutionThisdependsontheFouriernumber.ThebiggertheFouriernumberthegreaterthenumberofdatapointsperHzofthespectrumandthehigherthedigitalresolution.See“Processing”.DPDirect-polarisation.Anexperimentinwhichthenucleitobeobservedareexciteddirectly.dutycycleAvalueusedtoassesswhetheranexperimentmightdamagethespectrometer(orthesample).Thedutycycleshouldneverexceed20%(see“HowtoChooseaRecycleDelay”)dwellSpacingbetweendatapointsinthetime-domain.Candependonthewayacquisitionisimplementedbut,commonly,dwell=1/spectralwidth.endcapOpenrotorshavetobeclosedwithendcapsbeforetheycanbespun.FIDFreeInductionDecay(seefigure1).fieldMagneticfield,withfluxdensityquotedinT(Tesla)forthestaticmagneticfield(B0).Forthemagneticfieldassociatedwithanr.f.pulsethefluxdensityisgiveninmTor,moreusually,expressedasakHzequivalent(see“Matching”).flip-backExperimentalprocedureforshorteningrecycletimes(see“HowtoChooseaRecycle”).FouriernumberThenumberofpointsusedintheFT.Alwaysapowerof2.frequencydomainWhereinformationisdisplayedasafunctionoffrequency-thespectrumFTFourierTransform.Mathematicalprocesstoconverttime-domaintofrequency-domain.Designedtoworkwith2n(n=integer)datapoints.gainAmplificationappliedtothereceivedsignal.GaussNon-SIunitofmagneticfieldfluxdensity.TheSIequivalentisTesla(T),1T=10,000GintensityOnitsown-theheightofaline.Integrated-intensityistheareaundertheline.linebroadeningSpectracanbeartificiallylinebroadenedtoimprovetheirappearance.ThisinvolvesmultiplyingtheFIDwithadecayingfunctionpriortotheFT.See“Processing”.lineshapeTheshapeofindividuallinesinaspectrum.Commonly,GaussianorLorentzian(figure3)oramixtureofthetwo,areencounteredexperimentally.linewidthThisisusuallythefullwidthathalf-height(δν½)r.f.on-timer.f.on-time+r.f.off-timedutycycle=3©Solid-stateNMRService2001magic-angle54.7°or54°44´magnetisationwhendescribedclassically(non-quantummechanically)anensembleofspinsatequilibriuminanexternalmagneticfieldhasanetmagnetisationprecessingaboutanaxisalignedalongthatfield.magnetogyricratioSymbolγ.Afundamentalphysicalconstantofelementswithnon-zerospin.ForexampleγHis2.675x108rads-1T-1.matchShortforHartmann-Hahnmatch(see“Matching”)noisenormalisedintensitySignalintensitycanbemultipliedbyanarbitraryfactortogiveaparticularheighttothehighest(often)lineortheintegratedintensity.Oppositeofabsoluteintensity.nuclearspinquantumnumberSymbolI.Afundamentalpropertyofanucleus.OnlynucleiwithI0aresaidtobeNMR“active”.phase(1)Thephaseofapulserelatestoitspositioninthexyplaneoftherotatingframe.phase(2)ThephaseofaspectrallinecomesfromthewayinwhichtherealandimaginarycomponentsofacomplexFTarecombined(see“Processing”).phasecyclingThewayinwhichthephaseofapulse(orthereceiver)ischangedduringsuccessiverepetitionsofapulsesequence.Usedtosuppressartefactsandselectspecificcoherencepathways.ppmPartspermillion.Usualwayofreportin