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 | 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 | 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 | Keskin, A.Ü.

Article | 2003 | Asian Journal of Spectroscopy7 ( 2 ) , pp.93 - 96

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

Bayrakçeken, Fuat

Article | 2002 | Asian Journal of Spectroscopy6 ( 2 ) , pp.73 - 76

Ultraviolet light induced high resolution optical absorption spectra of high purity silicon dioxide have been studied. An ultraviolet discreate absorption spectra were recorded photographically between 200-300 nm. Resonance fluorescence was observed at 288.2 nm, and around this region, Raman resonance scattering were also recorded at room temperature by flash photolysis technique.

Bayrakçeken, Fuat | Keskin, A.Ü.

Article | 2004 | Asian Journal of Spectroscopy8 ( 1 ) , pp.9 - 14

Extinction coefficients, B-type delayed fluorescence and some photophysical properties of coronene in solution are studied by photolysis, flash photolysis, and laser flash photolysis techniques. For B-type delayed flourescence coronene molecules were excited in a two-step process. In the first step, an excited singlet S1 was created, which undergoes intersystem crossing to T1 state; then T-T absorption creates an excited triplet of coronene molecule, which returns to the first excited singlet level S1 by intersystem crossing from T2 to S1. The recreated first excited singlet state of coronene decays back to the ground state So by em . . .itting B-type delayed flourescence Daha fazlası Daha az

Bayrakçeken, Fuat | Güney, M. | Tarhanci, E.

Article | 2009 | Asian Journal of Spectroscopy13 ( 01.03.2020 ) , pp.15 - 20

Optical response of organic laser-dyes is often discussed considering unfortunately only two electronic energy levels. In the simplest case, the excited state potential surface is displaced along a number of normal coordinates. Vibrations involved in optical dynamics appear as resonance and are also Raman active. A single spectral density suffices to describe optical two-level dynamics of rigid molecules. The high frequency part is hardly distinguishable from the resonance Raman spectrum including proper conversion factors. The low frequency part is difficult to measure by Raman spectroscopy, so femtosecond pump-probe and stimulated . . . photon echo systems are better for structure elucidation Daha fazlası Daha az

Bayrakçeken, Fuat | Karaaslan, Ï.Ş.

Article | 2003 | Asian Journal of Spectroscopy7 ( 03.04.2020 ) , pp.125 - 128

The ultraviolet absorption and emissions as well as anti-Stokes Raman scatterings of spectroscopically pure triptycene was investigated by flash and laser flash photolysis technique in solution at room temperature and at 77°K. The whole spectrum, absorption, excitation, fluorescence, phosphorescence, T-T absorption, and Anti-Stokes Raman scattering spectra were recorded photographically and photoelectrically in the ultraviolet region. Scattered lines were observed at 360 and 380 nm, on phosphorescence spectrum at 77°K.

Keskin, A.Ü. | Bayrakçeken, Fuat

Article | 2004 | Asian Journal of Spectroscopy8 ( 2 ) , pp.63 - 71

This study concentrates on UV-VIS molecular flash spectroscopy techniques in which registered analog data are transferred into PC medium in a simple manner, so that information can be processed using well known mathematical software tools, such as MATLAB. Considering the characteristics of this kind of spectrographic data, wavelength scaling and some modified spectral smoothing methods, so called average of the moving average spectra and average of the moving median spectra (hereafter, AMAS and AMMS) are introduced and a method used for eliminating the effects of intense excitation source lines from the spectrogram are also describe . . .d as two applications of this study Daha fazlası Daha az

Bayrakçeken, Fuat | Topaloglu, S.

Article | 2002 | Asian Journal of Spectroscopy6 ( 2 ) , pp.77 - 80

The observation of triplet-triplet absorption of salicylidene-p-bromo aniline, 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 photographically 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.