Phosphorescence spectrum, basis

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 phosphorescence spectrum of 5, measured in 1967, exhibited maxima in 1,1-difluorotetrachloro-ethane at 530 and 537 nm, corresponding to triplet energies of about 54 kcal molNo attention has been paid to date to the photophysics (or photochemistry) of a,P-diketoesters. Emission from acyclic vic-tri- and tetraketones could not be detected with conventional equipment The phosphorescence maximum of 5,5-dimethylcyclohexane-l,2,3-trione (6) was suggested in 1971 to occur at about 615 nm ( phos < 0.001) on the basis of results obtained in a study of oxidation of the corresponding 1,3-diketone. ... 

The powerful role of the exitonic migration was proved on the basis of the luminescence and photosensitivity investigations [270]. The preliminary ultraviolet illumination of PAC increases the photosensitivity and decreases the luminescence. The experimental data are given in Fig. 40. One can see the redistribution of the maxima intensity in the spectra without changing their positions. Apparently ultra violet illumination promotes the photolysis of the weak coordination bonds. This leads to the changing of the polymer homolog content. Stimulated exciton dissociation on the ruptured bonds results in an increase in the photosensitivity and a luminescence decrease. The experiments carried out at 77 K show that in the luminescence spectrum of irradiated frozen PAC a new maximum appears with a position close to the phosphorescence maximum of diphenylbutadiene. So the rupture of weak coordination bonds under ultraviolet irradiation was proved. 

The microwave spectrum of SiCh formed by conproportionation of SiCU and solid Si has been recorded . The large asymmetry of the Cl nuclear quadrupole coupling tensor was accounted for by large rr-electron back-donation from Cl to Si. Emission from the products of reaction of excited P2,0 Ar atoms with SiCLj and with SiH2Cl2 in a EX2 discharge flow system has been attributed to phosphorescence from Bi SiCl2 on the basis of the vibrational spacings . 

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