Bayrakçeken, Fuat

Article | 2007 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy68 ( 1 ) , pp.143 - 146

The 12B2 › 32B2 transition in the absorption spectrum of the benzyl free radical has been recorded in the vapor phase together with a new band at shorter wavelengths, probably the first Rydberg band of the radical in the vapor phase. The photolysis flash was of short duration and it was possible to follow the kinetics of the radicals' decay, which occurred predominantly by bimolecular recombination. © 2006 Elsevier B.V. All rights reserved.

Bayrakçeken, Fuat

Conference Object | 2011 | Applied Physics B: Lasers and Optics105 ( 3 ) , pp.573 - 574

Ultraviolet light induced high resolution optical absorption spectra and resonance coherent fluorescence of spectroscopically pure fused silica have been studied, due to their potential applications in optoelectronics and laser flash spectroscopy for laboratory use, for optical fibers and for power optics for lasers. Ultraviolet discrete absorption spectra and resonance coherent fluorescence were recorded photographically between 200 and 260 nm. Resonance discrete and coherent fluorescence (i.e. lasing effect) were observed in the 250-255 nm band at room temperature by high photon flux excitation spectroscopy. © Springer-Verlag 2011.

Bayrakçeken, Fuat | Yaman, A. | Hayvali, M.

Article | 2005 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy61 ( 5 ) , pp.983 - 987

An ultraviolet light-induced photophysical and Photochemical changes of coumarin-481 in cyclohexane have been studied by photolysis technique at room temperature, due to its potential applications in photonics, photochemistry, and electronic spectroscopy. During the optical pumping, coumarin-481 showed photochemical changes, therefore as the concentration of coumarin-481 decreased, a photoproduct concentration increased rapidly. An absorption band of the product was observed at around 250 nm. Photoproduct emission spectra characteristics show that photoproduct molecules can also be used as a laser-dye at different emission frequency . . .. © 2004 Elsevier B.V. All rights reserved Daha fazlası Daha az

Keskin, S.S. | Aslan, N. | Bayrakçeken, Fuat

Article | 2009 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy72 ( 2 ) , pp.254 - 259

Structure elucidation of Coumarin-500 Laser-dye in cyclohexane at room temperature has been studied by UV-Vis, Raman, and FTIR spectroscopic techniques. Optical properties and chemical behavior under the influence of atmospheric positive electric pulsed corona discharges were also examined. The effects of UV-Vis irradiation changed some optical parameters, such as decrease in optical density on the absorption spectrum and formation of photoproducts, due to the chromaticity removal. No significant optical changes were observed in the light absorption upon UV-irradiation but large changes in absorption spectrum were observed after pos . . .itive electric corona discharge treatments, FTIR and Raman spectra in non-polar solvent are recorded and interpreted. © 2008 Elsevier B.V. All rights reserved Daha fazlası Daha az

Bayrakçeken, Fuat | Özceylan, M.

Article | 2002 | Asian Journal of Spectroscopy6 ( 3 ) , pp.119 - 123

Salicylindeneaniline originally crystallized from a solution has lemon yellow colour. Irradiation with near ultraviolet causes the colour change from yellow to red. The red state changes spontaneously back to yellow. This change is accelerated by visible light. Kinetic data are reported in the temperature range between 18.5 and 55°C, for the dark fading reactions of the coloured isomers formed by the ultraviolet irradiation. First order reactions were observed, activation energies and entropies of activation are reported. The observation of T-T absorption was complicated due to coloured isomer formation during the optical pumping.

Bayrakçeken, Fuat | Keskin, A.Ü.

Article | 2003 | Asian Journal of Spectroscopy7 ( 03.04.2020 ) , pp.137 - 141

Two forms of the title compound have been observed, one being colorless or light yellow, the other highly colored. The colorless form has structure (I), since the geometry of the spyro carbon requires that the rings be approximately at right angles to each other, effectively isolating the ? electrons of the seperate systems and restricting light absorption to the ultraviolet region of the spectrum. The thermal formation of colored species was measured by observing the increase in absorbance at 570 nm with an increase in temperature, 50°C. The solution was then allowed to stand for one hour permiting a reestablishment of equilibrium . . .and the absorption spectra was then recorded. The spectra in all cases were identical within experimental error. It has been shown that thermochromic and photochromic colors are in fact spectroscopically identical. The thermal transient decay followed first-order kinetics regardless of the wavelengths selected Daha fazlası Daha az

Bayrakçeken, Fuat

Article | 2009 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy71 ( 5 ) , pp.2026 - 2029

Photophysical and photochemical properties of diradical in the first excited state is recorded for the very first time with the IR, band structure for dianilino molecule at room temperature, in the vapor phase. In this experiment high resolution absorption spectra of anilino free radical, dianilino, aniline in the vapor phase and silicon dioxide in the solid state were recorded by flash photolysis technique photographically. Silicon dioxide absorption band between 250 and 255 nm were also observed for the reaction cell, because the cell and windows of the cell material were spectrosilica grade fused quartz. And this absorption band . . .also used as wavelength calibration for all the photoproducts formed in the reaction cell during optical pumping. © 2008 Daha fazlası Daha az

Bayrakçeken, Fuat

Article | 2008 | Asian Journal of Spectroscopy12 ( 4 ) , pp.121 - 130

Bayrakçeken, Fuat | Güney, M.

Article | 2010 | Asian Journal of Spectroscopy14 ( 01.02.2020 ) , pp.31 - 34

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.

Bayrakçeken, Fuat

Article | 2004 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy60 ( 4 ) , pp.923 - 925

Ultraviolet light induced high resolution optical absorption spectra and resonance fluorescence of spectroscopically pure fused silica have been studied, due to its potential applications in optoelectronics and flash (laser flash spectroscopy laboratory use), for optical fibers and power optics and lasers. An ultraviolet discrete absorption spectra and resonance coherent fluorescence were recorded photographically between 200 and 260 nm. Resonance discrete and coherent fluorescence were observed at 250-255 and 220-225 nm bands at room temperature by flash photolysis technique. © 2003 Published by Elsevier B.V.

Bayrakçeken, Fuat

Article | 2012 | Asian Journal of Spectroscopy ( SPEC. ISS. ) , pp.259 - 261

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.

Bayrakçeken, Fuat

Article | 2004 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy60 ( 13 ) , pp.3033 - 3036

High resolution S0 › Sn and T1 › Tn electronic absorptions and B-type delayed fluorescence of 1,2,7,8-dibenzanthracene in polymethylmethacrylate (PMMA) were experimentally observed by flash and laser flash photolysis technique. Dibenzanthracene molecules were excited in a two-step process. In the first step, an excited singlet is created, which undergoes intersystem crossing to triplet state, then T-T absorption creates an excited triplet dibenzanthracene molecule, which returns to the first excited singlet level by intersystem crossing. The re-created first excited singlet of dibenzanthracene decays back to the ground state by emit . . .ting B-type of delayed fluorescence, which was observed at the same emission band of prompt (normal) fluorescence, and R-, E-, P-types of delayed fluorescences. For normal fluorescence, S1 state is decaying to S0 ground state. For E- and P-type of delayed fluorescences, T 1 state is decaying to S0 via S1 state, and for B-type of delayed fluorescence, T2 state is decaying to S 0 via S1 state. © 2004 Elsevier B.V. All rights reserved Daha fazlası Daha az