Non-radiative decay rate

The photophysical properties of a xanthene dye have been extensively studied. In order to explain a relationship between the non-radiative decay rate constant (k r) of the dye and a solvent polarity parameter ( t(30)), Quitevis et al. proposed a two-state model [36,37]. According to the model, kot is given by... 

The experimentally determined emission decay rate /c xp of the higher lying triplet sublevel II is not only determined by the sir rate but also by the usual radiative and non-radiative decay rates of state II to the electronic ground state 0 with /cn 0 = 1/T - Thus, the sir rate is obtained by [24,60,65]... 

The non-radiative decay rate is as before (its spectral density is irrelevant here) and the total decay rate is therefore as before. The spectral density of the radiated (fluorescence) signal... 

In Figure 16.3, the excitation / relaxation electric fields that can interact with organic semiconductor are from the incident light field (E) and metal field (Em) for excitation and near metal surface quenching of non-radiative decay rates the radiative decay rate (F), metal radiative rate (F,), and metal radiative decay rate... 

Figure 19.1 (A) 2D projection of the calculated local field intensity distribution around a pair of 15 nm diameter silver nanoparticles excited with Xi = 400 nm light polarized along the interpaiticle axis. The edge-to-edge particle separation is 2 nm and the free space incident light intensity Ej,x P taken to be unity. The local field intensity near the pair is shown in false color. The calculation was done using dipole-dipole approximation (DDA) method with each dipole unit being a square with sides of 0.2 nm. (B) Model of the photophysics of a molecule represented by a three level system and how the excitation and decay dynamics are affected by plasmon enhancement of radiative rates and the introducticm of a rate for quenching Icq of the excited state due to proximity to the metal surface. E (X ) and E (X2) are the field enhancements at the position of the molecule for the excitation and emission wavelengths respectively, kn and kMR represent the radiative and non-radiative decay rates of the molecule in the absence of plasmon enhancement.

The decreased emission intensity and constant hfetime with pressure indicate that pressure is influencing the population of the state rather than its non-radiative decay rate. Webster and Drickamer developed a Dj excitation model based on feeding rates from the charge transfer state involved in the excitation process. According to the model [256,257], the Dj states are populated through transfer of excitation energy from the charge transfer state and depopulated by back transfer. Upon excitation, transfer occurs sequentially to the... 

The rate of energy transfer between the donor and acceptor, eret> is given by Eq. 2, where tq is the inverse decay rate of the donor, = ka = kj + (the sum of the radiative, k, and non-radiative decay rates, k, Rq is the Forster distance, and r is the distance separating the donor and acceptor. The Forster distance is... 

CF,)jC,H4, 0-, m-, and p-FC,H4Me, o- and m-FC,HiCF PhF, - CeFe, and C,F6H has been studied, and trends in the radiative and non-radiative decay rates of the excited molecules are discussed. - c/s-But-2-ene is effective in increasing the fluorescent and triplet yields of pentafluorobenzene. The decay rate of triplet benzophenone, produced by laser flash photolysis, is ca. ten times faster in hexafluorobenzene than in benzene, and reversible addition of the triplet species to the aromatic ring may play an important role. The phosphorescence spectrum of decafluoro-benzophenone has been studied, and the triplet state of this ketone (see also p. 380) in inert solvents e.g. perfluoromethylcyclohexane) has a lifetime of 20 ps. U.v. irradiation of decafluorobenzophenone in isopropyl alcohol... 

---