Fluorescence decay rates

Keiier R A 1998 Singie-moiecuie identification in flowing sampie streams by fluorescence burst size and intraburst fluorescence decay rate Anal. Chem. 70 1444-51... 

The significantly faster PuF6(g) fluorescence decay rate found using 532 nm excitation is unlikely to be due to a thermally induced effect (e.g. pyrolysis). The optical absorption coefficients of PuF6(g) at 532 nm is at most twice as large as at 1064 nm (15) Assuming the 1064 nm absorption... 

Kuhn et al. observed the fluorescence enhancement and fluorescence decay rate of a single terrylene molecule when a spherical gold nanoparticle was approached to the... 

To test the above ideas, Weitz etal.(i2) performed experiments on the fluorescence decay from a thin layer of europium(III) thenoyltrifluoracetonate (ETA) deposited on a glass slide covered with Ag particles approximately 200 A in diameter. The fluorescence decay rate was found to increase by three orders of magnitude in comparison with that of ETA in solid form. In addition to the large increase in decay rate, there was also evidence for an increase in overall fluorescence quantum efficiency. It is not possible from Eq. (8.11) to say anything about the manner in which is partitioned between radiative and nonradiative processes, y should be written in terms of a radiative part yr and a nonradiative part ynr y = yr + y r. Since the radiative rate for dipole emission is given by... 

In kinetic analysis of complex reactions, 210, 382 fluorescence decay rate distributions, 210, 357 implementation in Laplace de-convolution noniterative method, 210, 293 in multiexponential decays, 210, 296 partial global analysis by simulated annealing methods, 210, 365 spectral resolution, 210, 299. 

The quenching constant is kM/kf defined in Section It 1.2, where kM is the quenching rate constant in torr 1 sec 1 and kf is the fluorescence decay rate in sec 1... 

Instruments of this type may also be used quite effectively to evaluate kinetics of time-dependent changes in foods, be they enzymatic or reactive changes of other types. The computerized data-acquisition capabilities of these instruments allow precise measurement of absorbance or fluorescence changes, often over very brief time periods ( milliseconds). This is particularly useful for analysis of fluorescence decay rates, and in measurement of enzymatic activity in situ. A number of enzyme substrates is available commercially which, although non-fluorescent initially, release fluorescent reaction products after hydrolysis by appropriate enzymes. This kinetic approach is a relatively underused capability of computerized microspectrophotometers, but one which has considerable capability for comparing activities in individual cells or cellular components. Fluorescein diacetate, for example, is a non-fluorescent compound which releases intensely fluorescent fluorescein on hydrolysis. This product is readily quantified in individual cells which have high levels of esterase [50]. Changes in surface or internal color of foods may also be evaluated over time by these methods. 

Fig. 2.27. Stern-Volmer plots of DMABN fluorescence decay rates as a function of amine concentrations. TEA-triethylamine ABCO—quinuclidine IPEA—ethyldiiso-propylamine.98...

When decay curves were analyzed using a biexponential function, the nonradiative decay rate tsnr 1 of the slow component was evaluated by subtracting the radiative decay rate from the slow fluorescence decay rate. Figure 10 shows... 

Two techniques, phase and pulse fluorometry, are used for the direct measurement of fluorescence decay rates, and their principles are described by Birks and Munro (1967), Parker (1968), and Birks (1970). The photon sampling method has proved useful and versatile. This is an iterative technique in which single photons are counted as a function of the time at which they appear after excitation and a complete decay curve is built up. (For recent references see e.g. Zimmerman et al., 1973, 1974). Wider use of the photon sampling technique will increase the precision of lifetimes obtained and extend the range of compounds studied to those with shorter lifetimes or very low fluorescence yields. 

Note that if the radiative rate kf can be calculated, then the fluorescence decay rate and fluorescence lifetime follow from the fluorescence quantum yield (jy. Of course, the situation is often more complex. As will be described below, fluorescence decays for proteins often do not follow the single exponential decay model of Equation 2. The fluorescence quantnm yield and Equation 3 then provide an average fluorescence lifetime. 

In this approach, the excited-state lifetime of molecules is measured by following the decay of their fluorescence. The electron injection rate ( j) is calculated from the measured fluorescence decay rate (kobs) and the intrinsic radiative (kf) and non-radiative (A nr) excited decay rates through the relationship... 

In time-resolved fluorescence (TRF) (Maundrell et al., 1985), europium chelates are excited at 340 nm to emit two types of fluorescence, a shortlived background fluorescence (< 0.1 ms) and a fluorescence due to emitted photons of Eu " lasting up to over 1 ms. This difference in fluorescence decay rate can be exploited by measuring fluorescence only after background fluorescence has completely decayed to obtain a very high signal to noise ratio (detectability down to 10 5 M) as shown in Fig. 7.5. Originally, anti-hapten antibody was labeled with Eu " but in more recent procedures Eu " is directly attached to the nucleic acid (Sections 7.3.2.1 and 7.8.1). 

Nature of the Aggregates. The aggregates are hydrophobic, loose structures with some residual surface charge from the anionic polymer. The fluorescence decay rate constants k of pyrene in aggregates of PMA and C TAB, are identical to corresponding rate constants the kj in micellar alkyltrimethylammonium chloride,... 

A. Electron-Phonon Interaction Parameterization Scheme. In observing the fluorescence decay rate from a given J-manifold, it is generally found that the decay rate is independent of both the crystal-field level used to excite the system and the level used to monitor the fluorescence decay. This observation indicates that the crystal-field levels within a manifold attain thermal equilibrium within a time short compared to the fluorescence decay time. To obtain this equilibrium, the electronic states must interact with the host lattice which induces transitions between the various crystal-field levels. The interaction responsible for such transitions is the electron-phonon interaction. This interaction produces phonon-induced electric-dipole transitions, phonon side-band structure, and temperature-dependent line widths and fluorescence decay rates. It is also responsible for non-resonant, or more specifically, phonon-assisted energy transfer between both similar and different ions. Studies of these and other dynamic processes have been the focus of most of the spectroscopic studies of the transition metal and lanthanide ions over the past decade. An introduction to the lanthanide work is given by Hiifner (39). 

Figure 13. Vapor-phase absorption spectra (top) and excitation energy dependence of fluorescence decay rate (bottom) for /f-naphthylamine. (From ref. [4] with permission.)...

Case I [(A ,+A o)/ +this case we find that the preexponential constant in (6) is positive and that the A(l) fluorescence signal rises with the rate of the X decay, namely [(A ,+ A o)P +A xj X2l-Consequently, a plot of either the decay rate of X fluorescence or the rise rate of A(l) fluorescence vs. pressure of A gives a line whose slope is (A, + Aq). The decay of the A(l) signal takes place at the rate kyP, so that a plot of this rate vs. gives a line whose slope is Ay. Finally k can be obtained, for example, from a plot of the X fluorescence decay rate vs. 

The only polyatomic molecule for which energy transfer from I has been adequately examined is water. Grimley and Houston have measured as a function of Fh o DjO the rates for (a) the decay of I fluorescence, (b) the rise and decay of total H2O stretching fluorescence, and (c) the rise and decay of the (002) (001) stretching fluorescence. The 1 fluorescence decay rate was also measured as a function of Since... 

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