Browsing by Author "Maras, I"

Now showing 1 - 11 of 11
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    Spin-isospin transitions in chromium isotopes within the quasiparticle random phase approximation
    Cakmak, S; Nabi, JU; Babacan, T; Maras, I
    Beta decay and electron capture on isotopes of chromium are advocated to play a key role in the stellar evolution process. In this paper we endeavor to study charge-changing transitions for 24 isotopes of chromium (Cr42-65). These include neutron-rich and neutron-deficient isotopes of chromium. Three different models from the QRPA genre, namely the pn-QRPA, the Pyatov method (PM) and the Schematic model (SM), were selected to calculate and study the Gamow Teller (GT) transitions in chromium isotopes. The SM was employed separately in the particle particle (pp) and pp + particle-hole (ph) channels. To study the effect of deformation, the SM was first used assuming the nuclei to be spherical and later to be deformed. The PM was used both in pp and pp + ph channels but only for the case of spherical nuclei. The pn-QRPA calculation was done by considering both pp and ph forces and taking deformation of nucleus into consideration. A recent study proved this version of pn-QRPA to be the best for calculation of GT strength distributions amongst the QRPA models. The pn-QRPA model calculated GT distributions had low-lying centroids and small widths as compared to other QRPA models. Our calculation results were also compared with other theoretical models and measurements wherever available. Our results are in decent agreement with previous measurements and shell model calculations. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.
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    The Isospin Admixture of The Ground State and The Properties of The Isobar Analog Resonances In Deformed Nuclei
    Aygor, HA; Cakmak, N; Maras, I; Selam, C
    Within quasiparticle random phase approximation (QRPA). Pyatov-Salamov method for the self-consistent determination of the isovector effective interaction strength parameter, restoring a broken isotopic symmetry for the nuclear part of the Hamiltonian, is used. The isospin admixtures in die ground state of the parent nucleus; and the isospin structure of the isobar analog resonance (IAR) state are investigated by including the pairing correlations between nucleons for Kr72-80 isotopes. Our results are compared with the spherical case and with other theoretical results.
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    Calculation of the log(ft) values for the allowed Gamow- Teller transitions in deformed nuclei using the basis of Woods-Saxon wave functions
    Salamov, DI; Kücükbursa, A; Maras, I; Aygör, HA; Babacan, T; Bircan, H
    The present study investigates the log(ft) values of the allowed beta(+/-) decay between odd-A deformed nuclei in the atomic mass regions of 125 less than or equal to A less than or equal to 131 and 159 less than or equal to A less than or equal to 181. Single particle energies and wave functions have been calculated with a deformed Woods-Saxon potential. Calculations have been performed within the framework of a proton-neutron quasi-particle random phase approximation (QRPA), including the schematic residual spin-isospin interaction between nucleons in the particle-hole and particle-particle channels. It has been seen that the results obtained by using the values for the fixed particle-hole and particle-particle interaction strengths, chi(GT)(ph) = 5.2/A(0.7) MeV and chi(GT)(pp) = 0.58/A(0.7) MeV, have good agreement with the experimental observations.
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    Quadrupole moments of some doubly-even molibden nuclei and the onset of collectivity
    Turkan, N; Ibis, I; Maras, I
    A good description of the quadrupole moments is obtained by investigating 94,96,98,100,102,104,106,108Mo isotopes in terms of the interacting boson model. After the positiveparity states and electromagnetic-transition rates B(E2) of even-mass Mo nuclei were calculated it was seen that there is a good agreement between the obtained results and some previous experimental data. At the end of the quadrupole moment calculations it was proved that the results agree well with the previous experimental data.
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    E(5) BEHAVIOUR OF THE Ge ISOTOPES
    Turkan, N; Maras, I
    The sufficient aspects of model leading to the E(5) symmetry have been proved by presenting E(5) characteristic of the transitional nuclei (64-80)Ge. The positive parity states of even-mass Ge nuclei within the framework of Interacting Boson Model have been calculated and compared with the Davidson potential predictions along with the experimental data. It can be said that the set of parameters used in an calculations is the best approximation that has been carried out so far. Hence, Interacting Boson Approximation (IBA) is fairly reliable for the calculation of spectra in such set of Ge isotopes.
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    Microscopic interacting boson model calculations for even-even 128-138Ce nuclei
    Turkan, N; Maras, I
    In this study, we determined the most appropriate Hamiltonian that is needed for the present calculations of energy levels and B(E2) values of Ce128-138 nuclei which have a mass around A congruent to 130 using the interacting boson model (IBM). Using the best-fitted values of parameters in the Hamiltonian of the IBM-2, we have calculated energy levels and B(E2) values for a number of transitions in Ce-128,Ce-130,Ce-13 2,Ce-134,Ce-136,Ce-138. The results were compared with the previous experimental and theoretical (PTSM model) data and it was observed that they are in good agreement. Also some predictions of this model have better accuracy than those of PTSM model. It has turned out that the interacting boson approximation (IBA) is fairly reliable for calculating spectra in the entire set of Ce-128,Ce-130,Ce-132,Ce-134,Ce-136,Ce-138 isotopes and the quality of the fits presented in this paper is acceptable.
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    Preliminary results of Sr/Ca ratio study of teeth samples by photoactivation analysis
    Kavun, Y; Bortosun, I; Maras, I; Dapo, H; Segebade, C
    In this paper, we have performed Photoactivation Analysis (PAA), a non-destructive method, which is used to determine elemental concentration of any sample. This paper presents the first use of this method in medical sciences in Turkey. The method was applied to the determination of Sr/Ca ratios in teeth. The collected teeth samples and standards (SrO and CaCO3) have been irradiated for a fixed time interval with high energy photons. The photons were generated by a clinical linear accelerator (cLINAC). The photon end-point energy was 18 MeV. The energy and the time interval were sufficient to achieve good activation. Afterward, the samples and standards have been analysed with gamma spectroscopic analysis by using an HPGe detector system. By analysing many samples, a database of Sr/Ca ratios will be created at Nuclear Research and Application Center (NUBA). In this paper we present a small subset of the already analysed data as an example of our capabilities and goal. We hope to set an example for future studies.
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    The isospin admixture of the ground state and the properties of the isobar analog resonances in medium and heavy mass nuclei
    Salamov, DI; Babacan, T; Kücükbursa, A; Ünlü, S; Maras, I
    Within the framework of quasiparticle random phase approximation (QRPA), Pyatov-Salamov method [23] for the self-consistent determination of the isovector effective interaction strength parameter, restoring a broken isotopic symmetry for the nuclear part of the Hamiltonian, is used. The isospin admixtures in the ground state of the parent nucleus, and the isospin structure of the isobar analog resonance (IAR) state were investigated with the inclusion of the pairing correlations between nucleons for the medium and heavy mass regions: 80 < A < 90, 102 < A < 124, and 204 < A < 214. It was determined that the influence of the pairing interaction between nucleons on the isospin admixtures in the ground state and the isospin structure of the IAR state is more pronounced for the light isotopes (N approximate to Z) of the investigated nuclei.
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    The effect of the pairing interaction on the energies of isobar analogue resonances in 112-124Sb and isospin admixture in 100-124Sn isotopes
    Babacan, T; Salamov, D; Kücükbursa, A; Babacan, H; Maras, I; Aygör, HA; Ünal, A
    In the present study, the effect of the pairing interaction and the isovector correlation between nucleons on the properties of the isobar analogue resonances (IAR) in Sb112-124 isotopes and the isospin admixture in Sn100-124 isotopes is investigated within the framework of the proton-neutron quasi-particle random phase approximation (pnQRPA). The form of the interaction strength parameter is related to the shell-model potential by restoring the isotopic invariance of the nuclear part of the total Hamiltonian. In this respect, the isospin admixtures in the Sn100-124 isotopes are calculated, and the dependence of the differential cross section and the volume integral J(F) for the Sn(He-3,t)Sb reactions at E(He-3) = 200 MeV occurring by the excitation of IAR on mass number A is examined. Our results show that the calculated value for the isospin mixing in the Sn-100 isotope is in good agreement with Colo et al's estimates (4-5%), and the obtained values for the volume integral change within the error range of the value reported by Fujiwara et al (53 +/- 5 MeV fm(3)). Moreover, it is concluded that although the differential cross section of the isobar analogue resonance for the (He-3,t) reactions is not sensitive to pairing correlations between nucleons, a considerable effect on the isospin admixtures in N approximate to Z isotopes can be seen with the presence of these correlations.
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    Determination of the Sr/Ca ratio of tooth samples by photoactivation analysis in Southern Turkey
    Kavun, Y; Boztosun, I; Dapo, H; Maras, I; Segebade, C
    A nuclear analytical technique, namely instrumental photon activation analysis (IPAA), was used to determine Sr and Ca concentrations in human teeth. This work was conducted using the first accelerator facility, an off-shelf clinical linear accelerator (cLINAC), in Turkey. The tooth samples supplied by the Akdeniz University Faculty of Dentistry were analyzed for determination of the Sr/Ca element ratio. The results were obtained to demonstrate the impact of socioeconomic changes on dietary habits. A calibration material (CM; a mixture of calcium and strontium oxides) was required for quantification of the analytical results. The tooth samples, together with the CM, were exposed to 18 MeV end-point energy bremsstrahlung photons from the cLI-NAC. Thereafter, the gamma-ray spectra of the samples and the CM were obtained using high resolution gamma spectroscopy. Variations in the Sr/Ca ratio in the teeth of patients fed with beef and fizzy beverages were investigated in this study.
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    THE INVESTIGATION OF EVEN-EVEN 114-120Xe ISOTOPES BY THE FRAMEWORK OF IBA
    Maras, I; Gümüs, R; Türkan, N
    In this work, the ground state, quasi beta and quasi gamma band energies of Xe-114,Xe-116,Xe-118,Xe-120 isotopes have been investigated by using the both (IBM-1 and IBM-2) versions of interacting boson model (IBM). In calculations, the theoretical energy levels have been obtained by using PHINT and NP-BOS program codes. The presented results are compared with the experimental data in respective tables and figures. At the end, it was seen that the obtained theoretical results are in good agreement with the experimental data.