POPOP molecule

The 3700A wavelength photons interact and excite the POPOP molecules. The POPOP in... 

The excited POPOP molecules go to the ground state via the emission of photons with... 

The 3700A wavelength photons interact and excite the POPOP molecules. The POPOP in this case is called the secondary fluor or the -wavelength shifter, and... 

The excited POPOP molecules go to the ground state via the emission of photons with average wavelengths of 4200A These photons can be efficiently used to eject photoelectrons at the photocathode of the photomultiplier tube ... 

In most cases, the linear absorption is measured with standard spectrometers, and the fluorescence properties are obtained with commercially available spectrofluo-rometers using reference samples with well-known <1>F for calibration of the fluorescence quantum yield. In the ultraviolet and visible range, there are many well-known fluorescence quantum yield standards. Anthracene in ethanol (Cresyl Violet in methanol (commonly used reference samples for wavelengths of 350-650 nm. For wavelengths longer than 650 nm, there is a lack of fluorescence references. Recently, a photochemically stable, D-ji-D polymethine molecule has been proposed as a fluorescence standard near 800 nm [57]. This molecule, PD 2631 (chemical structure shown in Fig. 5) in ethanol, has linear absorption and fluorescence spectra of the reference PD 2631 in ethanol to... 

In Fig. 12 in Ref 25, fluorescence microscopy images of different dye-loaded zeolite L single crystals are shown. Each line consists of three pictures of the same sample, but with different polarizations of the fluorescence observed. In the first one, the total fluorescence of the crystals is shown, and in the others, the fluorescence with the polarization direction indicated by the arrows is displayed. The zeolite was loaded with the following dyes (A) Py+, (B) PyGY", (C) PyB +, (D) POPOP (see Table 1). Most crystals show a typical sandwich structure with fluorescent dyes at the crystal ends and a dark zone in the middle. This situation can be observed when the diffusion of the dyes in the channels has not yet reached its equilibrium situation. It illustrates nicely how the molecules penetrate the crystals via the two openings on each side of the one-dimensional channels. 

Liquid scintillation counting is usually carried out using organic solvents such as toluene which are readily excited by ft particles. The number of solvent molecules, and hence fluorophores exdted depends on the energy of the ft particles. It is in principle possible to determine the phosphorescence of the excited solvent molecules directly however, this phosphorescence is at short wavelength (Imix < 300 nm) and is therefore not readily accessible technically. The fluorophore most often used is 2,5-diphenyloxazole (PPO) with an emission maximum of 380 nm, either alone or in combination with a secondary fluorophore such as l,4-bis-(5-phenyloxazole)-benzene (POPOP) whose fluorescence maximum... 

The solvent used is usually an aromatic hydrocarbon (toluene or xylene are most common), or sometimes dioxan. The scintillator is a polyaromatic fluorophore, such as 295-Diphenyloxazole (PPO). In the past it has sometimes been necessary to add a secondary scintillator to which the energy is transferred from the primary scintillator. Secondary scintillators, of which 2,2 -(l,4-Phenylene)bis-[5-phenyloxazole] (POPOP) is the most well known, are somewhat larger molecules, with more delocalisation than the primary scintillators they emit at longer wavelengths at which photomultiplier tube sensitivity is greater. 

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