Exciplex Formation Accompanied with Excitation Quenching

Abstract

The competence of the reversible exciplex formation and parallel quenching of excitation (by electron or energy transfer) was considered using a non-Markovian pi-forms approach, identical to integral encounter theory (IET). General equations accounting for the reversible quenching and exciplex formation are derived in the contact approximation. Their general solution was obtained and adopted to the most common case when the ground state particles are in great excess. Particular cases of only photoionization or just exciplex formation separately studied earlier by means of IET are reproduced. In the case of the irreversible excitation quenching, the theory allows specifying the yields of the fluorescence and exciplex luminescence, as well as the long time kinetics of excitation and exciplex decays, in the absence of quenching. The theory distinguishes between the alternative regimes of (a) fast equilibration between excitations and exciplexes followed by their decay with a common average rate and (b) the fastest and deep excitation decay followed by the weaker and slower delayed fluorescence, backed by exciplex dissociation.

Highly efficient exciplex formation via radical ion pair recombination in X-irradiated alkane solutions for luminophores with short fluorescence lifetimes

“…MFE in the emission band of exciplexes upon optical generation is well-known 28 and is based on the reversibility of transitions between the radical ion pair state and the exciplex in the solvent of the corresponding viscosity and polarity. [29][30][31][32][33][34][35][36][37] For systems lending themselves to exciplex formation, under ionizing irradiation MFE has so far only been observed in polar solvents, e.g. for the system pyrene/N,N-diethylaniline in methanol.…”

Screening of Exciplex Formation by Distant Electron Transfer

“…The account of the space dependence of the irreversible ionization rate is the major advantage of the present work compared to its precursor, 17 where the electron transfer was considered as a contact one. The difference between distant and contact electron transfer is especially pronounced when it is under diffusion control.…”

“…For the particular case of the contact transfer reaction, the corresponding kernels were calculated in ref 17. Note that in contrast to the kinetic equations (2.1a), (2.1c), and (2.1e) the general equations contain the additional second term in the right-hand side of eq 2.11 and a third term in the right-hand side of eq 2.12.…”

“…It was considered analytically in section IV.B1 of the preceding work. 17 It was shown there that one has to discriminate between two alternative limits:…”

Approaches to contactless optical thermometer in the NIR spectral range based on Nd 3+ doped crystalline nanoparticles

“…= W eq (T). The temperature dependence of the decay rate corresponds to the contribution of each level spontaneous decay rate according to their equilibrium population as per following expressions [10][11] …”