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 | Demir, O.J. | Karaaslan, I.S.
Article | 2007 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy66 ( 2 ) , pp.462 - 466
Garnets doped with Nd+3 have attracted extensive interests because of their applications in solid-state lasers, as well as upconversion luminescence and magneto-optical and magnetic properties. Usually, these properties are closely related to the local structures and properties of the Nd+3 impurities in the hosts. Since information about electronic states and local structures of the impurity Nd+3 in the garnets would be helpful to the understanding of the properties of these materials, theoretical investigations on the specific heat functions and the local structures for these Nd+3 centers are of significance. © 2006 Elsevier B.V. A . . .ll rights reserved Daha fazlası Daha az
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
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
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 | 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 | Aktaş, S. | Toptan, M. | Ünlügedik, A.
Article | 2003 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy59 ( 1 ) , pp.135 - 138
High resolution absorption spectra of anisole and phenoxyl radical has 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 radical's decay which occurred predominantly by bimolecular recombination. The concentration of the phenoxyl radical calculated from the concentration of diphenoxyl molecules formed in the reaction cell during the optical pumping. The absolute extinction coefficient of this radical was measured from the absorption band at 291 nm, and found to be 0.95 × 10+4 mol-1 . . .l cm-l. © 2002 Elsevier Science B.V. All rights reserved Daha fazlası Daha az
Article | 2007 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy66 ( 04.05.2020 ) , pp.1291 - 1294
Nd3+ doped scheelite type of crystals have attracted extensive interests because of their applications in solid state lasers, as well as upconversion luminescence and magneto-optical and magnetic properties. Usually, these properties are closely related to the local structures and properties of the Nd3+ impurities in the hosts. Since information about electronic states and local structures of the impurity Nd3+ in the scheelite crystals would be helpful to the understanding of the properties of these materials, theoretical investigations on the specific heat functions and the local structures for these Nd3+ centers are of significanc . . .e. © 2006 Elsevier B.V. All rights reserved Daha fazlası Daha az
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 | Telatar, Z. | Ari, F. | Tunçyürek, L. | Karaaslan, I. | Yaman, A.
Article | 2006 | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy65 ( 1 ) , pp.143 - 146
The ?-methallyl free radical is formed in the flash photolysis of 3-methylbut-1-ene, and cis-pent-2-ene in the vapor phase, and then subsequent reactions have been investigated by kinetic spectroscopy and gas-liquid chromatography. 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. The measured rate constant for the ?-methallyl recombination was (3.5 ± 0.3) × 1010 mol-1 l s-1 at 295 ± 2 K. The absolute extinction coefficients of the ?-methallyl radical are calculated from the optical densities of the absorption bands . . .. Detailed analysis of related absorption bands and lifetime measurements in the original ?-methallyl high-resolution discrete absorption spectrum image were also carried out by image processing techniques. © 2005 Elsevier B.V. All rights reserved Daha fazlası Daha az
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
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.
