Non-radiative decay channels

From the identical shape and position of the absorption spectra (not shown) in chloroform and polysulfone we conclude that the distribution of geometries of the Ooct-OPV5-CN molecules is the same in both situations. In polysulfone, the non-radiative decay channel is effectively inhibited and a normal single-exponen-... 

Non-Radiative Decay Channels - 1064 nm Excitation. We turn now to a comparison of the observed fluorescence photon yield defined by Equation 1 and the expected fluorescence quantum yield of the 4550 cm 1 state which indicates that several non-radiative decay channels may be open following 1064 nm excitation of PuF6(g) The following relationship between... 

If near-field is to be used as a measurement tool for intrinsic fluorescence properties, then one needs to know the operating conditions or samples that are appropriate for lifetime and/or spectroscopic measurements. To address this question, the FDTD method was used to compute the spectral shift and fluorescence lifetime as a function of the tip-sample gap with the molecule directly under the center of the aperture. Fig. 18 shows these results. For a yg of about 3 x 10 /s, the frequency can red shift by about 10 GHz for distances less than 50 nm. This frequency shift is not important at room temperature where the vibronic bands are approximately 10 GHz wide. At low temperatures, the linewidths are in the 0.01 to 10 GHz range, and probe-induced frequency shifts should be measurable. The frequency dependence on distance was not calculated at the larger distances, 200-400 nm, relevant to the experiment of Moerner et al. [11] (Section 2.4.2). On the other hand, the fluorescence lifetime of high quantum yield molecules was predicted to be affected in first order throughout the near-field region. Bian et al. [25] point out that for systems with fast non-radiative decay channels, the perturbations by the probe may not be significant. 

The article is organized as follows. First a review of the fluorescence process will be given, with a detailed analysis of what happens when a fluorophore is in the vicinity of a particle. It will be shown that both the incident field and radiated fields may be enhanced, thereby tending to produce increased fluorescence. However, we will also see that the particle opens additional non-radiative decay channels and these can serve to quench the fluorescence. Following this a discussion of some recent experiments relating to fluorescence will ensue. A general theorem relating enhanced absorption and emission will be proved in the appendix. 

There may be other non-radiative decay channels not described by the optical properties of the solid. For example, if the excited molecule were touching the nanoparticle then there could be energy transfer by the short range contact interaction. There could also be the tunneling of an electron from the excited molecule to the solid, if the energy of the excited electron lies above the Fermi energy of the metal. 

Inter-molecular non-radiative decay channels in thin films... 

The second group of indirect detection methods concerns the excited states of low fluorescence yield. In that case, higher sensitivity is expected from observation of the non radiative decay channels. In diatomic molecular ions two main channels are to be... 

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