Fluorescence lifetime studies

Thus it is possible to obtain k from a graph of 4>/°// vs. [Q] or from a fluorescence lifetime study,... 

Until recently there were comparatively few reports of fluorescence lifetime studies of dye molecules in the near-IR, but this situation has changed rapidly. The fluorescence lifetimes of near-IR emitting dyes such as carbocyanines, porphyrins, oxazines, and xanthenes, are usually in the nanosecond region, consistent with the high oscillator strength of the Si-So transition in such compounds. 

N. Barboy and J. Feitelson, Fluorescence lifetime study of the denaturation of ribonuclease... 

This review will be concerned with fluorescent-lifetime studies upon condensed systems (that is, glasses, liquids, or crystals) containing rare-earth ions, and will to a large extent deal only with trivalent ions pumped by optical means. Laser phenomena themselves will not be considered, because a number of very excellent review articles (5-7) and books (8, 9) already exist on this subject. 

IV. RESULTS OF FLUORESCENT-LIFETIME STUDIES A. Introductory Remarks... 

We suggest the following possible reasons for the absence of anion emission in these experiments First, it is possible for water and methanol to form adducts with CO2 which might inhibit their ability to solvate the proton. This possibility was checked using water as a cosolvent in supercritical ethylene, which will not interact with water data do not indicate formation of an anion therefore solvent/cosolvent adducts are not a plausible explanation. Second, perhaps the anion is being formed but is quenched very efficiently. The anion species would be more susceptible to quenching than the neutral molecule. This possibility could be investigated in principle with fluorescence lifetime studies, but this has not been done. It is entirely possible that the anion emission is so weak as to be hidden underneath the tail of the neutral emission. 

Smith, J.A., West, R.M., and Allen, M. 2004. Acridones and quinacridones novel fluorophores for fluorescence lifetime studies. J. Fluoresc. 14, 151-171. 

The metallated PDA (6a) and the metal-free polymer have previously been investigated using picosecond-resolution fluorescence lifetime studies and a picosecond characterization of the two photon absorption coefficent, p the latter has... 

In more recent work in our laboratory, fluorescence lifetime studies on a series of South Florida riverine to marine water samples (Shark River in Everglade National Park to Florida Bay in the Gulf of Mexico) also indicated that several fluorophores are present, with multiple lifetimes in the range of... 

FLUORESCENCE LIFETIME STUDIES OF CYANOBACTERIAL PHOTOSYSTEM II MUTANTS... 

Fluorescence Lifetime Studies of Cyanobacterial Photosystem II Mutants 667... 

There are also two detector devices that are gaining popularity for fluorescence lifetime studies due to their fast time response the microchannel plate photodetectors and streak cameras. MicroChannel plate photodetectors, similar to PMTs, are based on the use of multiplication of photoelectrons. Instead of using discrete dynodes, continuous semiconductor-coated glass multiplier tubes of 10 pm diameter... 

Deters, B., Burrows, J.P., Orphal, J. UV-visible absorptitm cross sections of bromine nitrate determined by photolysis of Br0N02/Br2 mixtures. J. Geophys. Res. 103, 3563-3570 (1998) Donnelly, V.M., Kaufman, F. FluOTescence lifetime studies of NO2. n. Dependence of the perturbed B2 state lifetimes on excitation energy. J. Chem. Phys. 69,1456-1460 (1978) Donnelly, V.M., Keil, D.G., Kaufman, F. Fluorescence lifetime studies of NO2. IB. Mechanism of fluorescence quenching. J. Chem. Phys. 71, 659-673 (1979)... 

The scope of fluorescence lifetime studies The kinetics of fluorescence decay... 

Van der Auweraer, M., Holzwarth, A. R., and Connolly, J. S. (1987) Charge separation in carotenopoiphyrin-quinone triads Synthetic, conformational and fluorescence lifetime studies, J. Am. Chem. Soc. 109, 846-856. 

Bazan and coworkers investigated the emission behavior of [2.2]paracyclophane-based compounds [48-55], They reported two types of emission mechanisms for [2.2]paracyclophane-based compounds, i.e., emission from the monomer state and emission from the phane state (excimer-like emission). The conjugation length of the stacked n-electron system, the extent of overlap, and the orientation between the stacked n-electron systems determine the mechanism. According to the photoluminescence spectra of 13 and 19 (Fig. 5) and their high d>pL (0.82 for 13 and 0.86 for 19), the emission of the [2.2]paracyclophane-based x-stacked polymer occurred from the monomer state. Fluorescence lifetime studies supported this hypothesis. Both fluorescence decay curves of 13 and 19 were a single exponential, and the fluorescence lifetime (r) of the polymer was 1.27 ns (j = 1.14), which was identical to the lifetime of 19 (r= 1.24 ns,1.00) [30]. 

Fluorescence lifetime studies have been also performed in the NdAl2 Cl6,H 3 vapor complex(es) (Krupke 1976b, Jacobs et al. 1977). The Nd F /2 state was populated via a rapid non radiative process subsequent to optical excitation at 531 nm performed by means of a Nd rYAG laser. The authors then monitored fluorescence intensities from the Nd + F3/2 —> I9/2 and F3/2 —> " ll 1/2 transitions and determined fluorescence lifetimes they discussed several mechanisms accounting for non-radiative deactivation and for the observed temperature dependence of the measured radiative lifetimes. 

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