Yazar "Kilic, H. S." seçeneğine göre listele
Listeleniyor 1 - 7 / 7
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Analysis of the xylenol isomers by femtosecond laser time of flight mass spectrometry(CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS, 2018) Kepceoglu, A.; Koklu, N.; Gundogdu, Y.; Dereli, O.; Kilic, H. S.Xylenol is a phenolic chemical substance having two methyl groups and one hydroxyl group attached to a benzene ring and has six isomers. 2,4-xylenol is the only isomer of the xylenol molecule that is in the liquid phase while the remaining isomers are all in crystal form at room temperature. In the scope of this study, we have experimentally investigated ionization and dissociation properties of xylenol isomers. All experiments were carried out by using a time of flight mass spectrometry (TOF-MS) system coupled with a femtosecond laser system. The laser pulse power-dependent multiphoton ionization of xylenol isomers was investigated by using IR (800 nm) femtosecond laser pulses having a pulse width of similar to 90 fs in duration and laser intensities changing from 2.6 x 10(13) to 2.6 x 10(14) W/cm(2). Theoretically, molecular orbitals (LUMO+1, LUMO, HOMO, HOMO-1), vertical and adiabatic ionization energies were calculated using density functional theory (DFT) with B3LYP functional and 6-311++G(d,p) basis set by following geometry optimization and performing conformational analysis.Öğe Calculation of the 1s-2s two-photon excitation cross-section in atomic hydrogen(SPRINGER, 2008) Celik, G.; Celik, E.; Kilic, H. S.The two-photon excitation cross-section of atomic hydrogen is calculated using explicit summation over intermediate states within the framework of dipole approximation. The matrix element for two-photon excitation is transformed into finite sums, consisting of the product of a radial and angular part. Nine intermediate states are employed in the calculation of the transition matrix element. The two-photon excitation cross-section obtained for the transition 1s(2)S(1/2)-2s(2)S(1/2) in atomic hydrogen is a good agreement with the literature.Öğe Determination of excited-state ionization Potentials for lithium-like sequence using weakest bound electron potential model theory(POLISH ACAD SCIENCES INST PHYSICS, 2007) Celik, G.; Yildiz, M.; Kilic, H. S.In this work, the theoretical calculation of excited-state ionization potentials for Is(2)2p(2)P(1/2), 1s(2)3s(2)S(1/2), 1s(2)3d(2)D(1/2), 1s(2)4s(2)S(1/2), 1s(2)4p(2)P(1/2), and 1s(2)4d(2)D(1/2) iso-spectrum series of lithium-like elements were carried out using a weakest bound electron potential model theory for nuclear charges from Z = 3 to Z = 18. The Breit-Pauli approximation was used for relativistic contributions. The obtained values are compared with the experimental results from literature. The overall agreement between data obtained in this work and experimental data from literature can appear to be quite good being generally within 0.1% of experimental values.Öğe Molecular Structure and the EPR Calculation of the Gas Phase Succinonitrile Molecule(AMER INST PHYSICS, 2017) Kepceoglu, A.; Kilic, H. S.; Dereli, O.Succinonitrile (Le. butanedinitrile) is a colorless nitrile compound that can be used in the gel polymer batteries as a solid-state solvent electrolytes and has a plastic crystal structure. Prior to the molecular structure calculation of the succinonitrile molecule, the conformer analysis were calculated by using semi empirical method PM3 core type Hamiltonian and eight different contbrmer structures were determined. Molecular structure with energy related properties of these confomiers having the lowest energy was calculated by using DFT (B3LYP) methods with 6-311++G(4) basis set. Possible radicals, can be formed experimentally. were modeled in this study. EPR parameters of these model radicals were calculated and then compared with that obtained experimentally.Öğe The Onset of Coulomb Explosions in Polyatomic Molecules(1999) Smith, D.J.; Ledingham, K. W. D.; Singhal, R. P.; McCanny, T.; Graham, P.; Kilic, H. S.; Tzallas, P.; Kosmidis, C.; Langley, A. J.; Taday, P. F.With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 1015 and 1016W cm-2. For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to ~1016 W cm-2, parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart.Öğe Radiative Lifetimes of Rydberg States in Neutral Gallium(POLISH ACAD SCIENCES INST PHYSICS, 2009) Yildiz, M.; Celik, G.; Kilic, H. S.Radiative lifetimes were calculated using weakest bound electron potential model theory for 4s(2) ns S-2(1/2) (n >= 7), 4s(2) np P-2(1/2)0 (n >= 5), 4s(2) np P-2(3/2)0 (n >= 6), 4s(2) nd D-2(3/2)0 (n >= 6), 4s(2) nd D-2(5/2)0 (n >= 6) series in neutral gallium. The use of the quantum defect theory and Martin's expressions allowed us to supply lifetime values along by means of the series above. The results obtained in this work presented good agreement with theoretical and experimental values. Moreover, some lifetime values not existing in the literature for highly excited Rydberg states in gallium atom were obtained using this method.Öğe The theoretical calculation of transition probabilities for some excited p-d transitions in atomic nitrogen(SPRINGER, 2006) Celik, G.; Akin, E.; Kilic, H. S.The atomic transition probabilities are calculated for individual lines between some quartet terms of 3p -> 4d and 3p -> 5d transition arrays using weakest bound electron potential model theory (WBEPMT). In the determination of relevant parameters which are needed for calculation of transition probabilities; we employed numerical non-relativistic Hartree-Fock wave functions for expectation values of radius in both ground and excited states unlike to NCA method used on traditional WBEPMT procedure. We have obtained very good agreement between our results and the accepted values taken from NIST.
