Bayrakçeken, Fuat | Karaaslan, I.S.

Article | 2003 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy59 ( 12 ) , pp.2785 - 2789

High resolution electronic absorption spectra of aniline and anilino free radical have been recorded in the vapor phase at room temperature by flash photolysis technique, and subsequent reactions have been investigated by kinetic spectroscopy. It was possible to follow the kinetics of the anilino radical's decay which occurred predominantly by bimolecular recombination. Decay parameters of anilino free radical were measured from the absorption bands. © 2003 Elsevier Science B.V. All rights reserved.

Bayrakçeken, Fuat | Telatar, Z. | Ari, F. | Bayrak, A.B.

Article | 2007 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy67 ( 5 ) , pp.1276 - 1280

The radicals formed in the flash photolysis of 2-methylbut-1-ene and subsequent reactions have been investigated by kinetic spectroscopy and gas liquid chromatography. Less than 10% of photo products are formed by a molecular made of fission of the excited olefin, and of the radical modes the relative probabilities of band fission, ß(C{single bond}H):ß(C{single bond}H):?(C{single bond}C) are 13:1.37:1. The extinction coefficients of ß-methallyl radical measured experimentally for all the absorption bands. The decay of the ß-methallyl radical was second order. The rate constant for the ß-methallyl radical recombination experimentally . . . measured was 2.6 ± 0.3 × 1010 l mol-1 s-1 at 295 ± 2 K. The spectrum image showing the absorption bands was examined by image processing techniques in order to improve the visual experience of each band by localizing to a specific region of interest. Experimental results illustrate how the exact location of absorption bands was clearly extracted from the spectral image and further improvements in the visual detection of absorption bands. © 2006 Elsevier B.V. All rights reserved Daha fazlası Daha az

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

Bayrakçeken, Fuat | Demir, O.J. | Tunçyürek, L. | Karaaslan, I.S.

Article | 2006 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy65 ( 1 ) , pp.27 - 31

In principle the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the different relaxation channels. Initially, electronically excited naphthalene emits photons in the phosphorescence band of naphthalene and these emitted photons are absorbed by the acceptor molecule biacetyl, then excited biacetyl phosphoresces. In this investigation, sensitized phosphorescence decay times in different conditions were measured for naphthalene-biacetyl system in the vapor phase. The ultraviolet-visible spectrum of biacetyl vapor at room temperature c . . .onditions was broad and structureless. © 2005 Elsevier B.V. All rights reserved Daha fazlası Daha az

Karaaslan, I.S. | Bayrakçeken, Fuat

Article | 2007 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy68 ( 5 ) , pp.1379 - 1381

The observation of triplet-triplet absorption of salicylidene-p-toluidine, is complicated by the possible colored isomer formation during the optical pumping. The short-lived (singlet-singlet) and long-lived (triplet-triplet) absorption spectra were recorded phographically by microsecond flash and nanosecond laser flash photolysis techniques. Salicylidene-aniline complexes were purified by repeated recrystallisation until further recrystallisation produced no further changes for X-ray diffraction pattern and optical absorption, emission properties. © 2007.

Bayrakçeken, Fuat

Article | 2007 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy66 ( 04.05.2020 ) , pp.1267 - 1270

p-Xylene sensitized biacetyl fluorescence and phosphorescence has been investigated and photosensitized phosphorescence lifetimes of biacetyl in the vapor phase has been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, due to primarily, it is believed, to the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature. © 2006 Elsevier B.V. All rights reserved.

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

Article | 2005 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy61 ( 9 ) , pp.2109 - 2114

o-Xylene sensitized biacetyl fluorescence and phosphorescence have been investigated and photosensitized fluorescence and phosphorescence lifetimes of biacetyl in the vapor phase have been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, primarily due to, it is believed, the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature. © 2004 Elsevier B.V. All rights reserved.

Bayrakçeken, Fuat

Article | 2008 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy71 ( 2 ) , pp.603 - 608

In principle the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the different relaxation channels. Initially, electronically excited benzophenone emits photons in the phosphorescence band of benzophenone and these emitted photons, as a stream of particles, are absorbed by the acceptor molecule naphthalene, then excited naphthalene phosphoresces. In this investigation, sensitized phosphorescence decay times in different conditions were measured for benzophenone-naphthalene system in the vapor phase. The ultraviolet-visible spectra o . . .f the system in the vapor phase at room temperature conditions were broad and structureless. © 2008 Elsevier B.V. All rights reserved Daha fazlası Daha az

Bayrakçeken, Fuat

Article | 2008 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy69 ( 1 ) , pp.222 - 224

https://hdl.handle.net/20.500.11831/3902

Bayrakceken, F.

Article | 2005 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy61 ( 6 ) , pp.1069 - 1074

In principle, the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the relaxation channels. Initially, electronically excited naphthalene emits photons and these emitted photons are absorbed by the acceptor molecule biacetyl, then excited biacetyl fluoresces. In this investigation radiative energy transfer-time is measured in cyclohexane by one and two-photon excitations. The UV-vis spectrum of biacetyl vapor at room temperature conditions was broad and structureless. © 2004 Elsevier B.V. All rights reserved.

Bayrakçeken, Fuat | Ari, F. | Telatar, Z.

Article | 2005 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy62 ( 04.05.2020 ) , pp.1151 - 1156

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 (hereafter DBA) 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 grou . . .nd state by emitting 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. The spectrum image showing the absorption/emission bands mentioned was also examined by image processing techniques in order to improve the visual experience of each band by localizing to a specific region of interest (ROI). Experimental results illustrate how the exact location of emission/absorption bands was clearly extracted from the spectral image and further improvements in the visual detection of absorption/emission bands. © 2005 Elsevier B.V. All rights reserved Daha fazlası Daha az

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

Article | 2007 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy67 ( 03.04.2020 ) , pp.762 - 766

X-ray, ultraviolet, and visible light induced photophysical changes of coumarin-540A in ethanol have been studied by the joint applications of X-ray, ultraviolet, and visible spectroscopy. Some impurities were found by X-ray fluorescence measurements. During the high power optical pumping, coumarin showed photochemical changes. Photoproduct emission spectra characteristics showed that photoproduct molecules can also be used as a laser dye at a different emission frequency in the ultraviolet region. © 2006 Elsevier B.V. All rights reserved.