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specialconditionintheseexperimentswastherecordingoffluorescence
spectrainlow-temperatureglassesorhighlyviscoussolvents,inwhichthe
motionsofthesedyesaswellasoftheirsurroundingsolventmoleculeswere
restrictedorretarded.IndependentlysimilarresultswereobtainedbyGalley
andPurkeyinCanada(Galley&Purkey1970).Theseauthorsworkedwith
differenttypesoffluorophores,indoleandtryptophan,possessingtheirexci-
tationspectrainthenear-UVregion.Comparisonoftheresultsobtainedon
differenttypesoffluorophorescouldsuggestgeneraloriginoftheseob-
servedeffects.
InitiallyanobservationmadeatthesametimebyG.Weber(Weber
&Shinitzky1970)stoodasideofthesefindings.Providingfluorescencepo-
larizationmeasurementsovertheexcitationspectrumofhighlyconcentrated
dyesolutionsinsolventglassheobservedthattheexcited-stateenergy
homotransfer(resonancetransferwithinpopulationofidenticalmolecules)in
thissystemvanishesatthered-edgeexcitation.Thesefindingswereimme-
diatelyconfirmedandextendedbyseverallaboratoriesinBelarus(Gulis
&Komyak1977),andsoonitbecameevidentthatalltheobservedphenom-
enahavethesameorigin.Thisnotionhavegotastrongersupportafterre-
portingbyTominetal.andPavlovich(Tominetal.1975,Pavlovich1976)on
thedependenceofexcitationspectraonemissionwavelengthinthesame
conditionsofsolidsolventenvironment.
Thestrongtemperaturedependenceofobservedeffects,sothattheyap-
pearathighviscositiesandbecomemaximalbelowthetemperaturesof
glasstransitioninthesolvent,suggestedtheirconnectionwiththerates
ofdielectricrelaxationofthemedium(Azumietal.1976).Thisnotioncorre-
latedwiththeresultsonexcitationenergyhomotransferandsuggestedthe
originofbotheffectsininhomogeneousbroadeningofthespectra(Gulis
&Komyak1977,Voropayetal.1980).Theapplicationoftime-resolvedspec-
troscopybroughtnewresults:themovementsoftime-resolvedspectradue
tosolventrelaxationcandependonexcitationwavelength(Nemkovichetal.
1980a).Thesemovementsstoptooccuratthered-edge,sothatinthefaran-
ti-Stokesregiontheycanevenproceedwiththeincreaseofexcited-state
energy(“up-relaxation”).Temporaleffectswerealsorecordedinexcitation
energyhomotransfer(Nemkovichetal.1981),indicatingthatthetransfer
proceedsinasystemwithdistributionofsolvent-soluteexcitationenergies
from“blue”emittingto“red”emittingfluorophoresandthisflowofenergy
stopsatthered-edge.
Thus,thenumberofimportantobservationswasaccumulatedwithtime
thatwasdetectedforavarietyoffluorophoresandindifferentmediawith
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