29Raman evidence for premelting in the [1].alpa. and .beta. phases of oleic acid.

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1、5080J.Phys.Chem.1988,92,5080-50821Ilifetimeisdeterminedbythetripletcharacteroftheexcitedmixedsinglet-tripletstates.ItisbelievedthatthenonradiativerateoftheTl-Sointersystemcrossingsteeplydependsonthevibrationalenergy.'Onthebasisofthisexpectation,westatethatthePEspectrummaybeex

2、ponentiallyreducedatE,>2000cm-'.AsENERGYRESOLVEDPHOSPHORESCENCETomeretal.'usedadelayedgatingofmorethan1,us,atripletier:3728inonradiativelifetimeof0.5hscanresultinmorethananorderofmagnitudereductionofanytransitioninthisenergyrange.Wealsonotethattheimplicationoftheexpectedtripl

3、etlifetimereductionalsopertainstotheidentificationofhotbandsandtheexistenceandlocationofthesecondtripletelectronicI11II370039004100430045~0Inthecaseofpyrazine,lifetimemeasurementcannothelpinWAVELENGTHCi)identificationofthetripletfromthesinglethotbandsexceptifFigure1.Energy-re

4、solvedphosphorescenceofpyrazine.Pyrazinewasabiexponentialdecayisobserved(asindeedmeasuredbyTomerexcitedattheQbranchofitslowesttripletstate(Aexzz3728A)inaetal.)asthelifetimeofthesingletisdeterminedbyitstripletpulsedplanarsupersonicjet.Thephosphorescenceisdispersedwith10-8,char

5、acter.resolution(800-rmslits).Theexistenceandlocationofthesecondtripletstateinpyrazineisstillanopenquestion.observationisinterpretedintermsoftheexpectedtripletnon-radiativedecaytothegroundstate.Thetripletlifetime4058cm-'Acknowledgment.ThisresearchwassupportedbytheIsraelabovei

6、tsorigin(atthesingletorigin)wasmeasuredbySmalleyAcademyofScience.Wethank0.SneandProf.0.Cheshnovskyandco-workers'tobe-350nsandwithaweakvibrationalenergyforstimulatingdiscussions.dependence.FromtherotationalindependenceofthenonradiativeRegistryNo.Pyrazine,290-37-9.decayoftheSI(

7、'B3,,)state,*itwasconcluded9thatthis350-11s(9)Amirav,A.Chem.Phys1986,108,403.(10)Hochstrasser,R.M.;Marzzacco,C.J.Chem.Phys.1968.49,1971;(7)Dietz,T.G.;Duncan,M.A.;Pulu,A.C.;Smalley,R.E.J.Chem.InMolecularLuminescence;Lim,E.C.,Ed.;W.A.Benjamin:NewYork,Phvs.1982.86.4026.Smallev.R

8、.E.J.Phvs.Chem.1982.86.3504.1969;p63.'(8)Saigusa,'H.;Lim,E.C.j.'Chem