Circularly polarized fluorescence spectra

Figure 4. Circularly polarized fluorescence spectra of I-O (broken line) and 1-2 (solid line) in dimethylformamide.

Fig. 11.23 a PL (fluorescence) spectra and b CPL (ot CPF, circularly polarized fluorescence) spectra of (/f)-Poly-10 cast films. The wavelength of excitation light for fluorescence was 380 nm. The inset shows photographs of the emitting film of the open form and the quenching film of the PSS of (7 )-Poly-10 (excitation wavelength A = 370 nm, 4 W, handheld lamp). Reprinted with permission from [20], Copyright 2010, Wiley... 

One characteristic feature of excimers in the polypeptide I-O and 1-2 is that they emit circularly polarized light [43,51]. Circularly polarized fluorescence (CPF) spectroscopy measures the difference in fluorescence intensity of the left and right circularly polarized component. Usually the CPF spectrum is plotted with Kuhn s circular dissymmetry factor, as the... 

Measurements of the circularly polarized fluorescence (CPF) of this compound (PPA) as a function of temperature indicate the existence of two kinds of excimers one with a negative CPF dissymmetry with an emission maximum around 460 nm and predominant at higher temperatures, the other with a positive CPF dissymmetry emitting at wavelengths longer than 500 nm and mainly formed at lower temperatures (Egusa et al., 1985). In the emission spectrum of poly-N -(9-carbazolyl)-carbonyl-L-lysine, even four distinct species are observed besides the emission of locally excited carbazole. 

Figure 9.29 Two-photon fluorescence excitation spectrum of 1,4-difluorobenzene. The upper and lower traces are obtained with plane and circularly polarized radiation, respectively, but the differences are not considered here. (Reproduced, with permission, Ifom Robey, M. J. and Schlag, E. W., Chem. Phys., 30, 9, 1978)...

The J sublevels of rare earths are split by ligand fields of low symmetry. These splittings may be observed in circularly polarized luminescence (CPL) but not in the fluorescence spectrum. Hence CPL spectra provide information on the rare earth ion and thus throw light on the binding site. The emission and CPL spectra of Tb3+ bound to transferrin and cobalbumin were found to be similar leading to the conclusion that the structure and... 

Fluorescence-detected circular dichroism (FDCD) is a chiroptical technique in which the spectrum is obtained by measuring the difference in total luminescence obtained after the sample is excited by left- and right-circularly polarized light. For the FDCD spectrum of a given molecular species to match its CD spectrum, the luminescence excitation spectrum must be identical to the absorption spectrum. 

Many features of the emission spectrum can show time dependence, including the spectral shape (l,3 (v-9), the peak intensity, the linear polarization (10) and, in principle, the circular polarization (11). In extreme cases, the emission spectrum can actually have two separate fluorescence bands from two different isomers of the electronically excited molecules (12-15). For molecules with this behavior, it is possible to determine the kinetics of excited state isomerization by transient emission spectroscopy. 

The degree of absorption polarization and the ratio of the extinction coefficient and exhibits a sharp increase starting at about 29,000 cm . Tliis indicates that a weak transition, namely the L j-transition, is buried below the much stronger L -band at wavelengths above 29,000 cm". A comparison of the absorption polarization spectrum, the fluorescence polarization spectrum and the circular dichroism spectrum shows that the 0-0-vibrational band of the L transition is located at about 29,000 cm [7]. This example demonstrates the usefulness of the liquid crystal method to localize weak hidden optical transitions. 

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