Journal of lominescence 24/25 (1981) 457—460 457 North-Holland Publishing Conspany CRITICAL EXCITON ANNIHILATION: OIFFUSION~ PERCOLATION OR ANOERSON TRANSITION?* P. W. Klymko and P. Kopelmnn~ Department nf Chemintry, Univernity of Michigan, Ann Arbor, Mi 48109, U.S.A. Goeat—Gueat Triplet-Triplet annihilation in highly porified mixed oryntala of naphthalene (goent)— naphthalene—d 8(hoat) waa atodied at 1.8 K via apec- trally and time—reaolved phonphorencence and delayed— flooreacence. We find nignificant deviationa from ourrent diffuaion theoriea and homogeneooa kinetion hot connintency with local heterogeneitiea (clonte— rization) and dynamic exciton percolation, an well nn with long—range annihilation (via noperexchnnge) There in negative evidence for nn Andernon trannition. The trnnnport of excitntionn in dinordered media han neveral intere- nting nnpectn: 1) Potential obnervntion of an Andernon—Mott tranni— tion [1]. 2( Tentn of corrent theorien on diffunion in dinordered media [2—4] . 3) Search for the effectn of local heterogeneitien (‘clontern’( and their relation with critical phenomena [5]. 4) Simple, reproducible, nyntemn for ntudying the principlen of heterogeneoun kineticn and interface renctionn. 5) The ponnibility of obtaining bio— mimetic nyntemn. 6( The ntudy of energy upconvernion via long-range annihilation (exciton funion) The ntendy—ntnte excitntion (Xe lamp) of highly purified inotopic mixed nnphthnlene cryntaln (C10H8 in C10D8 at 1.8 K) in nhuttered—off and npectrally renolved phonphorencence 1 0-0 1 nnd delayed fluoren- cence (0u_512(decnyn are monitored an n function of time, light inteonity gueut (C10H8) concentration etc. Cryntnln with 0.1 % mole guent nhow no delayed fluorenceoce (time renolution m 1 me] and junt normal trip- let decay curven (r = 2.7 n( . All hont homofunion, heterofunion, prompt fluorencence, rndintive trnpping, ioternyntem cronning etc. are over within 1 mn nod no guent homofunion taken place. However, guent— guent homofunion (triplet—triplet nnoihilntioo( in the phenomenon ntudied at higher guent coocentrationn. The negligible importance of any third channel of decay (i.e. nupertrappiog by impuritien or X- trnpn) wan demoontrated both npectroncopicnlly nod kioetically (Fig. 1). The abnolute and relative delayed fluorenceoce (DF) and phonphorencence (P) rnten were ntudied an a function of light (3 or— dern of magnitude) and time. An explicit example of n DF decay curve in given in Fig. 1. * Supported by WTH Grant 2 P01 MS 08116-1OA1 + Viuitiog Profeenor, Phynik, lout. 3, Uoiv. of Stuttgart, D — 7000 Stuttgart—SO, W.—Germnoy O 022—2313/81 /0000—0000/$02.75 © Norgh-Holland