The flash photolysis of dilute (3.5 × 10-4 M) oxygen-free solutions of ?1-salicylidene aniline in methyl alcohol, ?1 - salicylidene - p - chloro - aniline, ?1 - salicylidene - p - anisidine, and ?1 - salicylidene - p - toluidine in ethyl alcohol, has been investigated. Intense, colored transients are produced in the wavelength region 410-520 nm. The transients have been attributed to isomers formed by a hydrogen transfer from the o-hydroxy group to the bridge nitrogen atom. First order decays are observed for the dark fading reactions of the colored isomers formed by the ultra-violet irradiations.
Some photophysical and photochemical properties of 5H-dibenzo(a,d) cycloheptene have been measured including anti-Stokes scattering, prompt fluorescence, B-type of delayed fluorescence, phosphorescence and T1 - Tn absorption spectra. Quantum yield and decay parameters for the triplet state as a function of temperature have also been measured. The results are discussed and compared to those of molecules with similar structures and decay time of B-type fluorescence is reported here for the first time for dibenzocycloheptene. Stokes and anti-Stokes Raman scattering is observed on phosphorescence spectrum at 77K in methylcyclohexane.and . . . anti-Stokes Raman scattering is observed very strongly on phosphorescence spectrum
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Rubrene nanocystal is a red colored polycyclic aromatic hydrocarbon. It exhibit prompt fluorescence lifetime of 16±lns, close to the natural lifetime and B-type of delayed fluorescence of 48±5 ns. Rubrene excited states can act as quenchers for the fluorescence. Increasing the laser power leads to a saturation of fluorescence and a reduction of its lifetime. Raman Stokes shift was observed at 670 nm in the fluorescence spectrum. The fluorescence emission spectrum of rubrene molecule in solution mirrors the shape of the absorption spectrum regardless of the excitation frequency.
A number of photophysical properties of the title compound have been measured including the prompt fluorescence, B-type of delayed fluorescence, triplet-triplet absorption at room temperature, Raman scattering and phosphorescence at 77 K. in methylcyclohexane. The quantum yield and decay parameters for the triplet state as a function of temperature have also been measured. The results are discussed and compared to those of molecules in similar structures. Raman lines were observed at 430 and 490 nm, with the Stokes and anti-Stokes shifts 30 nm, which were symmetrical around the peak of the phosphorescence at 460 nm.
Silicon atomic fluorescence was excited within a carbon atomiser by high voltage (12 kV) discharge technique. Silicon atoms in different rock samples were excited to the upper electronic energy levels, then excited silicon atoms returned to the ground state by emitting characteristic fluorescence lines. All fluorescence transitions observed were resonance lines. Fluorescence lines of silicon were observed at 250.69, 251.43, 251.61, 252.41 and 252.81 nm, as intense discrete emission lines. These emission lines were calibrated by iron arc and mercury arc emission spectra.
The observation of triplet - triplet absorption for the large molecules is complicated due to the possible presence of radicals which result from hydrogen abstraction from the solvent by the triplet state of the parent molecule. Two forms of the title compound have been observed, one being colorless or light yellow, the other highly colored. It has been shown that thermochromic and photochromic colors are infact spectroscopically identical. Thermal transient decay followed first-order kinetics regardless of the wavelength selected. T-T absorption peak observed at 525 nm.
High resolution, S0-› Sn and S n-› S0 electronic absorption and prompt fluorescence of 1,2,5,6-dibenzanthracene in polymethylmethacrylate were experimentally observed by flash and laser flash photolysis technique. In the first step, an excited singlet state is created by nanosecond optical pumping system, then electronically excited molecule returns to the ground state by emitting high resolution prompt fluorescence at the room temperature. The decay time of S 1 state was measured by laser flash photolysis system, and found to be 12±1 nsec.
A number of photophysical properties of dibenzosuberone have been measured by flash photolysis of high photon flux, (1024 photon/pulse), excitation spectroscopy including prompt fluorescence, P and B-type of delayed fluorescences, triplet-triplet absorption, triplet decay and Raman scattering. The results are discussed and compared to those of molecules with similar structures, at room temperature and above.
Solid phase of naphthalene was influenced by sonic (50- 6400Hz) irradiation at room temperature, but the supercooled liquids of naphthalene were independent of applied ultrasonic power. In optical observation, the fractal distribution of microstructures was observed, the sample, which solidified under ultrasonic irradiation without isothermal holding. These results were due to anomalous nucleation caused by the local pressure induced by ultrasonic waves.
The compound benzophenone is acting both as a singlet quencher and triplet sensitizer to the molecule coumarin in polar and non-polar solvents. Collisional and optical energy transfer mechanism of coumarin-benzophenone system is studied in solution at room temperature by flash and laser flash photolysis techniques. Ultraviolet light-induced photophysical and photochemical changes of coumarin studied due to its potential applications in photonics, optoelectronics, quantum electronics, photochemistry, and electronic spectroscopy. An absorption and emission bands around 255.5 and 470 nm, were observed for the photoproduct (cyclobutanes . . .) of coumarin
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Kinetic and spectroscopic investigation of anilino have been carried out by the method of flash photolysis using an apparatus of high light output, (10 24 photons/pulse) and short flash duration, (t=2 psec). Anilino was performed in vapor phase at room temperature and a new absorption band was observed. The decay of the radical was observed to be second order.
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