Zero‐Phonon Lines in the Luminescence Spectra of Impurity Organic Crystals and Electron–Phonon Interaction

Abstract

The temperature dependcnces of t.hn shapes, widths, positions, and intensities of the zerophonon lines in the fluorescence spcctra of 1.12-benzperylene and coronene in a normal hexano matrix are irivcstigated experirnentnlly. The results obtained are discirsqcd in terms of t h e theory of the electron-phonon interactionin Lhe inlpnrity crystals. Thest>rertgth of the impurity-mat,rix coupling in t>he systems studied is shown to he very snitill. At high tomperatures the zero-phonon linewidt,h is a resiilt~ of theRainan Ec-tttering of the lattice phonons by the impurity molccrrle. The estimation of the change i n normal mode frequencies upon the phototransition in the impurity molecule and the mixing of the initial state norrnsl modes of the crystal sliow that those values are small. The anharrnonicit,y of t,he c.ryst,al vibrations in t>he "soft" organic crystals iri contrast to the "hard" inorganic crystals is shown to play an important role and t o det.crmine considerably t,he zero-phonon line characteristics. M I I T~H C A B I I O C T C I ~~U~O H O H H I J~ ~1i111aii n riiewpax c&nyopec.r~eiwmi 1,12-%e~311ep~-IlCCJle~oBalIa TeMIIe~laTyJlIIaH ~ZIBIICIIMOCTIB $,O~I."ZhI, rUIl[3lliIhI, IIO.llOM!€iMfI PI .lle1121 Ii 1;OpOtieHa €3 MaTpZlIle H O P M~. J I h I I O~~ reKCaHa. 1 [OJIyqeHHhIe pe3yJIbTaTbI 06cy>rc~aK)TCII H21 OCHOBC Teopllll 3 . l I e~; T~~~€~-~~€ l O t I l i O I . O U3a€lMOflefiCTflHrI U IIIJLI-MeCHhlX I:pMCTa.llJl:lS. nOKa3aH0, 'IT0 €3 Ii3y.ieJIJJhIX CPi CTeMBX CMna CBH311 II1)Il-MeClIOiI MOJIeEyJIbI C OCHOBHhIM ICPLICT~~IIJIOM OYeIII, MBJIZi. n I p P i IILICOICHX TCMneI)a-TypaX IIIApLlIIa 6eC~OHHOIIOfi JIIIHLII1 OIIpeAeJIHeTcR H OCIIOUHOM paMaHOBCKiIIM paccemiiicM r1)oiIoHoH pcmeTIm Ha rIpmecHoii Monepryae. I l p o m s e n e m O l l e I l l i a I I~M~I I~H I I H IIaeToT rropl\ianI,abIx Irone6airmii II[JU 4oTonepexone R IIpPiMeCHOfi MOJIeKyJIe I4 CTenCHM CMeUIMBaHHR Il~pMaJILllhIX IWJle6alIklfi H lia9:lJIhHOM COCTOF3-FIHH CLiCTeMhI. n O H a 3 a 1 1 0 , TITO 3TLI H e J I M q l l H b I 1Ma.llL-I. S' CTaHOBXeHo, IITO a H r a I l M O -I I~M KpHcTannririecKiix iione6amnl B ,,mwKnx" opraHmecms iCpiicTannax B oTnmiie OT ,,TBep~bix" H~O~~~I I M Y~C K M X ~q m c~a n~i o~ mrpaeT cyruecTBeIrnyIo POJIh II R 3H2ltIIITeJ1hHOi~ CTeneHIl Onpene.lIHC!T CBOBCTl321 6eC@~IlolIHhIS JIIlHRfi.

Theory of Pure Dephasing in Crystals

“…Thus, in this review I discuss our (non perturbative) results for the pure dephasing problem. A number of excel lent reviews of the more traditional theoretical approaches, and of some relevant experiments, have appeared within the last decade or so (19)(20)(21)(22)(23)(24). In addition, we have recently reviewed our own work (25,26).…”

Impurity spectroscopy in glasses and disordered crystals: Inhomogeneous broadening and electron phonon coupling

“…Thermal shifts and broadening of optical transitions are easier to follow in crystalline solutions, without resort to selective spectroscopy or photon echo techniques [21,22,25,26]. However, line shifts have rarely been considered, mostly because of the dearth of pressure shift data.…”

“…Remarkably, linear EPC remains so weak in both perylene and OEP that the line broadening can be studied up to 150 K, with negligible interference of phonon wings (spectra not shown). Dephasing studies of many other chromophores may be severely complicated by phonon wing broadening and the emergence of anti-Stokes satellite bands [21][22][23][24]. Thus, quadratic EPC has been characterized for selected guest-host combinations with small HuangRhys factors [11,23,25,26].…”

“…Temperature effects on organic crystal spectra have been studied for a long time [21][22][23][24][25][26], sometimes in conjunction with thorough theoretical analysis [23,25,26]. However, the T shifts are rarely reported [21,25,26], and are usually treated without correction for the solvent shift caused by thermal expansion of matrix.…”

Selective laser spectroscopy of molecules and ions in solids: a history, fundamentals and applications

“…In particular, along with interaction of the electronic transition in impurity centers with acoustic phonons of the crystal matrix [30], we also considered the influence of local and quasi-local vibrations of an organic molecular matrix on the integrated ZPL intensity [51,52] and of the anharmonicity of matrix vibrations on the temperature shift of ZPLs [53]. Unlike inorganic crystals doped with ions, the influence of local and quasi-local vibrations and anharmonicity of crystal vibrations in impurity organic molecular crystals proved to be important [51][52][53]. These investigations are summarized in the review [54] and paper [55].…”