Phosphorescence ultraviolet absorption

Ultraviolet absorption spectra were obtained from a Cary 118C Spectrophotometer. Luminescence measurements were obtained from a Perkin-Elmer Model MPF-3 Fluorescence Spectrophotometer equipped with Corrected Spectra, Phosphorescence and Front Surface Accessories. A Tektronix Model 510N Storage Oscilloscope was used for luminescence lifetime measurements. Fiber irradiation photolyses were carried out in a Rayonet Type RS Model RPR-208 Preparative Photochemical Reactor equipped with a MGR-100 Merry-go-Round assembly. 

Photophysical Processes in Dimethyl 4,4 -Biphenyldicarboxy-late (4,4I-BPDC). The ultraviolet absorption spectrum of dimethyl 4,4 -biphenyldicarboxyl ate was examined in both HFIP and 95% ethanol. In each case two distinct absorption maxima were recorded, an intense absorption near 200 nm and a slightly less intense absorption near 280 nm. The corrected fluorescence excitation and emission spectra of 4,4 -BPDC in HFIP at 298°K shows a single broad excitation band centered at 280 nm with a corresponding broad structureless emission band centered at 340 nm. At 77°K, the uncorrected phosphorescence spectra shows a single broad structureless excitation band centered at 298 nm, and a structured emission band having maxima at 472 and 505 nm with a lifetime, t, equal to 1.2 seconds. 

S. Subramanian, J. B. A. Ross, L. Brand, and P. D. Ross, Investigation of the nature of enzyme-coenzyme interactions in binary and ternary complexes of liver alcohol dehydrogenase with coenzymes, coenzyme analogs, and substrate analogs by ultraviolet absorption and phosphorescence spectroscopy, Biochemistry 20, 4086-4093 (1981). 

High Performance Liquid Chromatography Electrophoresis Thin Layer Chromatography Ultraviolet and Visible Spectroscopy Fluorescence and Phosphorescence Atomic Absorption and Plasma Spectroscopy X-ray Methods Mass Spectrometry... 

Figure 4.5 Ultraviolet absorption and emission spectra of polynaphthyl methacrylate in chloroform at 298 K (1) absorption, (2) fluorescence, (3) and (4) delayed emission in tetrahydrofuran-ether at 77 K and phosphorescence Reprinted with permission from Macromolecules, 1973, 2,219, copyright 1973,...

Spectroscopy, aimual reviews of new analytical instmmentation from the Pittsburgh Conference on Analytical Chemistry and AppHed Spectroscopy. Analytical Chemisty, "Fundamental Reviews" (June 1994, June 1996), analytical appHcations of infrared, ultraviolet, atomic absorption, emission, Raman, fluorescence, phosphorescence, chemiluminescence, and x-ray spectroscopy. 

Schenk G. H. (1973) Absorption of Light and Ultraviolet Radiation. Fluorescence and Phosphorescence Emission, Allyn and Bacon, Boston. 

Figure 18-13 Physical processes that can occur after a molecule absorbs an ultraviolet or visible photon. S0 is the ground electronic state. S, and T, are the lowest excited singlet and triplet electronic states. Straight arrows represent processes involving photons, and wavy arrows are radiationless transitions. R denotes vibrational relaxation. Absorption could terminate in any of the vibrational levels of S,. not just the one shown. Fluorescence and phosphorescence can terminate in any of the vibrational levels of Sq.

It should not be supposed that crystal defects enter into the picture only as nuisances which the chemist seeks to avoid or eliminate. Actually, certain optical and electrical properties of oxides, sulfides, and halides have been found to depend strongly on the nature and extent of crystal defects. Indeed, semiconductivity, fluorescence (absorption of radiation and emission of less energetic radiation), and phosphorescence (delayed fluorescence) of some salts may be spectacularly increased, not only by a small stoichiometric excess of one of the constituents, but also by addition of very tiny quantities of a foreign ion. Perhaps the best known example is the case of zinc sulfide which, when precipitated from aqueous solution and dried at low temperatures, shows negligible fluorescence upon exposure to ultraviolet light. When the sulfide is heated to... 

Lowry, O. H., Rosebrough, N. J., Farr, A. L., and Randall, R. J. (1951). Protein Measurements with the Folin Phenol Reagent. J Biol Chem 193 265. Schenk, G. H. (1973). Absorption of Light and Ultraviolet Radiation, Fluorescence and Phosphorescence Emission. Boston Allyn and Bacon. 

Abstract Photochemistry is concerned with the interaction between light and matter. The present chapter outlines the basic concepts of photochemistry in order to provide a foundation for the various aspects of environmental photochemistry explored later in the book. Electronically excited states are produced by the absorption of radiation in the visible and ultraviolet regions of the spectrum. The excited states that can be produced depend on the electronic structure of the absorbing species. Excited molecules can suffer a variety of fates together, these fates make up the various aspects of photochemistry. They include dissociation, ionization and isomerization emission of luminescent radiation as fluorescence or phosphorescence and transfer of energy by intramolecular processes to generate electronic states different from those first excited, or by intermo-lecular processes to produce electronically excited states of molecules chemically different from those in which the absorption first occurred. Each of these processes is described in the chapter, and the ideas of quantum yields and photonic efficiencies are introduced to provide a quantitative expression of their relative contributions. 

Wavelengths longer than 220 nm. The absence (2) of fluorescenci or phosphorescence in carbon suboxide excited in the ultraviolet would suggest that it is efficiently photodecomposed in this region of the spectrum. From its structural similarity to ketene, it is expected that this will involve production of C2O in step 1. The work of Bayes has in fact shown that this is the most probable process in the absorption region with a maximum at 265 nm. Bayes (11) found that photolysis of 02/02 mixtures led to production of allene rather than the acetylene, which is known (12) to be formed by insertion of carbon atoms into C2H. ... 

Direct methods of analysis such as ultraviolet (UV) absorption, infrared spectroscopy (IR), fluorescence, phosphorescence [13], X-ray fluorescence [14-16] and thermal analysis [17] have been reported. However, these methods generally lack specificity [18]. In Fourier transform IR (FTIR), overlapping bands of other species may interfere with the absorbance bands of the analyte, and in UV analysis the absorbance bands of different antioxidants can be very similar. UV and FTIR analysis are especially useful techniques when an antioxidant system is already known. X-ray fluorescence and elemental analysis are fast and useful techniques for the determination of antioxidants containing phosphorus or sulfur. The measurement of oxygen consumption... 

Optical spectroscopic methods are based on six phenomena (1) absorption, (2) fluorescence. (. ) phosphorescence. (4) scattering. (5) emission, and (6) chemiluminescence. Although the instruments for measuring each differ sontetehat in configurai ion, nio.sl of their ha -sic components are remarkably similar f urthermore, the required properties of these components are the same regardless of whether they are applied to the ultraviolet. visible, or infrared portion of the spectrum. ... 

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