Luminescence phosphorescence spectra

The phosphorescence spectrum ofthe primary electron donor is illustrated for Rb. sphaeroides in Fig. 15 (B). Phosphorescence from the Rb. sphaeroides reaction center complex with the quinones removed was detected at 20 Kon the long-wavelength side ofthe fluorescence and displayed an emission band with a maximum at 1318 nm (or 7590 cm ) and a half bandwidth of240 cm. The ratio of the integrated intensities of this 1318-nm luminescence to that ofthe fluorescence was, as expected, quite small, only... 

Phosphorescence Spectra.—Luminescence from a low-lying triplet state of water368 has been reported. It has been shown that two long-lived emission systems in the biacetyl crystal described previously by Sidman and McClure (see ref. 368) are in fact due to impurities, and a complete analysis is presented of the true 3AU xAg phosphorescence. The zero-zero band in emission is found at 20 327 cm-1.135 A satisfactory account of the six characteristic bands in the phosphorescence spectrum of benzene has been given on the basis of pseudo-Jahn-Teller vibronic interactions between the lower 3Blu and 3Elu states in which two active vibrations in the pseudo-cylindrical approximation are considered.369 The phosphorescence spectra of anthracene,3700 coronene,8706 benzophenone in aqueous solution,371 pyrimidine derivatives,372 porphyrins,298 873 and crystalline charge-transfer complexes 374 have been reported. 

Since 1997, we have been using in our laboratory an intensified charge-coupled device (ICCD, Oriel model Instaspec V, with a minimum temporal gate of 2.2 ns) in a daily basis for time resolved luminescence studies. The detector has 512x128 pixels in a maximum spectral range of 200 to 900 nm. With a single laser pulse, a fluorescence or a phosphorescence spectrum can be instantaneously obtained, since the combined use of the delay unit and time gate enables one to separate prompt from delayed emissions. 

The luminescence of bovine a-lactalbumin at 77 °K has been compared with that of lysozyme. a-Lactalbumin has a fluorescence spectrum that shows vibrational fine structure, an abnormal phosphorescence spectrum, a high fluorescence phosphorescence ratio, and an abnormal phosphorescence decay these properties are due largely to the proximity of tryptophanyl residues to the disulphide linkages. 

Fluorescent and phosphorescent substances are excited into an unstable energy state by UV light. When they return to the ground state they release a part of the energy taken up in the form of radiation. The emitted radiation is less energetic than the light absorbed and usually lies in the visible part of the spectrum. Since absorption (excitation) and emission obey a linear relationship over a certain range a reduction in absorption leads to a reduction in the luminescence, too. 

Luminescence measurements on proteins occupy a large part of the biochemical literature. In what surely was one of the earliest scientific reports of protein photoluminescence uncomplicated by concurrent insect or microorganism luminescence, Beccari (64), in 1746, detected a visible blue phosphorescence from chilled hands when they were brought into a dark room after exposure to sunlight. Stokes (10) remarked that the dark (ultraviolet) portion of the solar spectrum was most efficient in generating fluorescent emission and identified fluorescence from animal matter in 1852. In general, intrinsic protein fluorescence predominantly occurs between 300 nm and 400 nm and is very difficult to detect visually. The first... 

Dependencies of luminescence bands (both fluorescence and phosphorescence), anisotropy of emission, and its lifetime on a frequency of excitation, when fluorescence is excited at the red edge of absorption spectrum. Panel a of Fig. 5 shows the fluorescence spectra at different excitations for the solutes with the 0-0 transitions close to vI vn, and vra frequencies. Spectral location of all shown fluorescence bands is different and stable in time of experiment and during lifetime of fluorescence (panel b)... 

TGA, iodometric, mid-IR, luminescence (fluorescence and phosphorescence) and colour formation (yellowness index according to standard method ASTM 1925) were all employed in a study of aspects of the thermal degradation of EVA copolymers [67], Figure 23 compares a set of spectra from the luminescence analysis reported in this work. In the initial spectra (Figure 23(a)) of the EVA copolymer, two excitation maxima at 237 and 283 nm are observed, which both give rise to one emission spectrum with a maximum at 366 nm weak shoulders... 

It is worth noting some historical aspects in relation to the instrumentation for observing phosphorescence. Harvey describes in his book that pinhole and the prism setup from Newton were used by Zanotti (1748) and Dessaignes (1811) to study inorganic phosphors, and by Priestley (1767) for the observation of electroluminescence [3], None of them were capable of obtaining a spectrum utilizing Newton s apparatus that is, improved instrumentation was required for further spectroscopic developments. Of practical use for the observation of luminescence were the spectroscopes from Willaston (1802) and Frauenhofer (1814) [13]. 

The value of the phosphorescence quantum yield can be determined by measuring the total luminescence spectrum under steady irradiation. If the fluorescence quantum yield is known then the phosphorescence quantum yield may be found by comparing the relative areas under the two corrected spectra. 

Excited-state lifetimes can be measured directly by monitoring the decay of luminescence, but impurities present affect both the lifetime and the luminescence spectrum. Also, because low temperatures are necessary for phosphorescence studies, the excited-state properties determined may differ from those at room temperature. 

Under short-waved UV lamp excitation (254 nm) visually observed luminescence of calcite is violet-blue with very long phosphorescence time of several seconds. Under long-waved UV lamp excitation (365 nm) calcite exhibits visually the same violet-blue luminescence as under 254 nm excitation, but long phosphorescence is not detected. Under short laser excitations, such as 266 and 355 nm, at 300 K calcite demonstrates intensive UV-violet emission band peaking at 415 nm with half-width of 55 nm (Fig. 5.76a). Excitation spectrum of this band is composed of short waved tail in the spectral range less... 

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