Reaction Rate Constants of Triplet Excitons in Naphthalene Single Crystals

Abstract

The temperature dependence of the decay of the delayed fluorescence in a naphthalene crystal doped with P-chloronaphthalene is measured. The results are analyzed in terms of the reaction kinetics comprising a term for the collision of a free exciton with an exciton trapped by P-chloronaphthalene (X-trap). The reaction rate constant between the free and trapped excitons is obtained and found to be larger than the reaction rate constants of the triplet exciton with another triplet exciton, a radical, and a guest anthracene molecule in naphthalene crystals. Assuming that the reaction rate constant between the free and trapped excitons is the value at the diffusion limit, the transition probabilities from the neighbouring pair of an exciton and an energy acceptor to the excited state of the energy acceptor are obtained and compared with the results of the analysis using Dexter's theory.Die Temperaturabhiingigkeit des Abklingens der verzogerten Fluoreszenz eines Naphtalinkristalls, der mit P-Chlonutphtalen dotiert wurde, wird gemessen. Die Ergebnisse werden mit Reaktionskinetik analysiert unter EinschluB eines Termes fur den StoB eines freien Exzitons rnit einem durch P-Chlornaphtalen getrapten Exziton (X-Trap). Die Reaktionsrate zwischen den freien und getrapten Exzitonen wirderhalten, und es wirdgefunden, daB sie groler ale dieReaktionsrate eines Triplett-Exzitons mit einem anderen Triplett-Exziton, einem Radikal und einem GastAnthrazenmolekiil in Naphtalinkristallen ist. Unter der Annahme, daB die Reaktionsrate zwischen den freien und getrapten Exzitonen der Wert an der Diffusionsgrenze ist, werden die Ubergangswahrscheinlichkeiten von den Nachbarpaaren eines Exzitons und einem Energieakzeptor zu den ageregten Zustiiinden des Energieakzeptors erhalten und mit Egebnissen einer Analyse mittels der Theorie von Dexter verglichen.

Singlet-Singlet Energy Transfer Along the Helix of a Double-Stranded Nucleic Acid at Room Temperature

“…This prevents detailed modelling. An approximate comparison with the dipole-dipole mechanism can be made, however, by using the value of 20 em -1 , which was calculated (58) for the exchange energy, U, in polydA [This value is very similar to those reported for adjacent aromatic molecules in crystals (59,60).] The rate constant of transfer w is given by (8)…”

Triplet exciton transport in isotopic mixed naphthalene crystals. I. Kinetic analysis of trapping and fusion

“…) then the decay rate constant slows to 100 S-I. This gives a free exciton density of 10-6 mole fraction as opposed to the [10][11] value calculated for the C g = 1.0 crystal. Thus, in crystals such as those used by Klymko and Kopelman,6,7 it is no longer appropriate to say that a free exciton is more likely to find a BMN site than to find a second free exciton.…”