Person: ALTUN, ZİKRİ
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ALTUN
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ZİKRİ
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Publication Open Access Dielectronic recombination data for dynamic finite-density plasmas - VI. The boron isoelectronic sequence(EDP SCIENCES S A, 2004-06) YUMAK YAHŞİ, AYŞE; Altun, Z; Yumak, A; Badnell, NR; Colgan, J; Pindzola, MSWe have calculated dielectronic recombination rate coefficients for 22 ions of the boron isoelectronic sequence, between C+ and Xe49+, within the generalized collisional-radiative framework, as outlined by Badnell et al. (2003). Calculations have been performed from both ground and metastable initial states, in both LS- and intermediate-coupling, allowing for Deltan = 0 and Deltan = 1 core-excitations. Results are presented and discussed for a selection of ions from the sequence. Results which are not presented here can be accessed from the Atomic Data and Analysis Structure (ADAS) database (Summers 2003) or from the Oak Ridge Controlled Fusion Atomic Data Center (http://www-cfadc.phy.ornl.gov). Comparison is made with the results of other existing theoretical calculations.Publication Metadata only Electron-impact ionization of atomic ions in the Na isoelectronic sequence(IOP PUBLISHING LTD, 2008) YUMAK YAHŞİ, AYŞE; Altun, Z.; Yumak, A.; Golcek, U.; Loch, S. D.; Pindzola, M. S.; Griffin, D. C.Electron-impact ionization cross-sections and rate coefficients for the Na-like ions Mg+, Ar7+, Kr25+, Sn39+, Xe43+ and W63+ are presented. The direct ionization cross-sections of 2s, 2p and 3s subshells are calculated within a configuration-average distorted-wave (CADW) method. In addition, excitation-autoionization contributions originating from the inner-shell excitations of the type 2s22p63s -> 2s22p53snl (n = 3-6) and 2s22p63s -> 2s2p63snl (n = 3-6) are calculated using both CADW and level-resolved distorted-wave (LLDW) methods. We include the branching ratios for the radiation damping of the autoionizing configurations and levels. The excitation-autoionization contributions are found to be quite large for the lighter ions. For the heavier ions the radiation damping of the excitation-autoionization contribution is found to be significant. We find that the distorted-wave results are in good agreement with available experimental measurements, which only exist for Mg+, Ar7+ and Xe43+. We also find that the computationally simple configuration-average calculations are in reasonable agreement with the computationally demanding level-resolved calculations for the excitation-autoionization contributions for all the Na-like ions studied. In addition, Maxwellian rate coefficients are produced from our cross-sections and are archived in a format useful for plasma modelers.Publication Metadata only Level-resolved distorted-wave cross-sections of electron impact ionization of Ar5+(Institute of Physics Publishing, 2009-11-01) YUMAK YAHŞİ, AYŞE; Yumak A., Yavuz I., Altun Z.Electron impact ionization cross sections of Ar5+ were calculated using configuration-average (CADW) and level-resolved (LRDW) distorted-wave methods. Direct ionization cross-sections of 2s, 2p, 3s and 3p subshells were calculated within a CADW approximation. The contributions from the excitation autoionization channels were evaluated assuming single excitations from the 2s, 2p, and 3s subshells and in both CADW and LRDW methods. The radiative stabilization of the excitation autoionization channels were found to reduce the excitation autoionization by a small amount. © 2009 IOP Publishing Ltd.Publication Open Access Dielectronic recombination data for dynamic finite-density plasmas - XIII. The magnesium isoelectronic sequence(EDP SCIENCES S A, 2007-11) YUMAK YAHŞİ, AYŞE; Altun, Z.; Yumak, A.; Yavuz, I.; Badnell, N. R.; Loch, S. D.; Pindzola, M. S.We have calculated total and partial final- state level- resolved dielectronic recombination ( DR) rate coe. cients for the ground and metastable initial levels of 21 Mg- like ions between Al+ and Xe42+. This is the final part of the assembly of a levelresolved DR database necessary for modelling dynamic finite-density plasmas within the generalized collisional-radiative framework. Calculations have been performed in both LS-and intermediate coupling, allowing for. n = 0 and. n = 1 core- excitations from ground and metastable levels. Complementary partial and total radiative recombination RR coeficients have been calculated for the same ions viz. Al+ through Zn18+, as well as Kr24+, Mo30+, and Xe42+. Fitting coeficients which describe the total RR and DR rate coeficients (separately) are also presented here. Results for a selection of ions fromthis sequence are discussed, and compared with existing theoretical and experimental results. A full set of results can be accessed from the Atomic Data and Analysis Structure (ADAS) database or from the Oak Ridge Controlled Fusion Atomic Data Center (http://www-cfadc.phy.ornl.gov/data_and_codes). The complexity of further M-shell sequences, both from the atomic and modelling perspectives, renders this juncture a natural conclusion for the assemblage of the partial database. Further M-shell work, has and will, focus more on total rate coe. cients, rather than partials, at least in the medium term.Publication Open Access Dielectronic recombination data for dynamic finite-density plasmas - XI. The sodium isoelectronic sequence(EDP SCIENCES S A, 2006-03) YUMAK YAHŞİ, AYŞE; Altun, Z; Yumak, A; Badnell, NR; Loch, SD; Pindzola, MSDielectronic recombination (DR) rate coefficients for 22 sodium-like ions, between Mg+ and Xe43+, forming magnesium-like ions have been calculated as part of the assembly of a level-resolved DR database necessary for modelling dynamic finite-density plasmas, within the generalized collisional - radiative framework. Calculations have been performed from both ground and metastable initial states, in both LS - and intermediate coupling, allowing for Delta n = 0 and Delta n = 1 core-excitations from ground and metastable levels. Partial and total DR coefficients have been calculated for Mg+ to Zn19+, as well as Kr25+, Mo31+, and Xe43+. Results for a selection of ions from the sequence are discussed in the paper and compared with existing theoretical and experimental results. A full set of results can be accessed from the Atomic Data and Analysis Structure (ADAS) database or from the Oak Ridge Controlled Fusion Atomic Data Center (http:// www-cfadc.phy.ornl.gov/data_and_codes).Publication Open Access Electron-Impact Ionization of Atomic Ions: Theoretical Results(IOP PUBLISHING LTD, 2009-11-01) YUMAK YAHŞİ, AYŞE; Loch, S. D.; Burgos, J. M. Munoz; Ballance, C. P.; Ludlow, J.; Lee, T. -G.; Fogle, M.; Pindzola, M. S.; Griffin, D. C.; Yumak, A.; Yavuz, I.; Altun, Z.; Orel, AE; Starace, AF; Nikolic, D; Berrah, N; Gorczyca, TW; Kamber, EY; Tanis, JAA brief overview is given of theoretical results for electron-impact ionization of atoms and ions. A description is given of the main theoretical methods, along with the databases where the data are archived. It is shown that for light species, ground and metastable ionization cross sections are in reasonable agreement with experiment when non-perturbative data are used for the near neutrals and distorted wave data are used for ions greater than a few times ionized. Some discrepancies between theory and experiment still remain for systems with open d and open p subshells. The sensitivity of ionization rate coefficients to the near threshold part of the ionization cross section is shown. The role of excited states in effective ionization rate coefficients is demonstrated and recent excited state ionization cross section results for H, He, He+, B2+ and Ne are presented.Publication Open Access Dielectronic Recombination in He-like, Li-like and Be-like Iodine and KLM Resonances(IOP PUBLISHING LTD, 2012-11-05) YUMAK YAHŞİ, AYŞE; Bleda, Erdi A.; Yumak, Ayse; Yavuz, Ilhan; Altun, Zikri; Williams, ID; VanDerHart, HW; McCann, JF; Crothers, DSFDR rate coefficients for He-like, Li-like and Be-like Iodine ions and KLM resonances are calculated using MCBP approximation.Publication Metadata only Two small thermodynamically stable organic dications(ELSEVIER, 2010) YUMAK YAHŞİ, AYŞE; Yumak, Ayse; Yavuz, Ilhan; Altun, Zikri; Trindle, CarlSmall multiply charged species may be long-lived without the benefit of stabilization by a medium, primarily owing to the Coulomb barrier that impedes both formation and dissociation of the systems. We extend the category of small organic dicationic structures that may possess thermodynamic stability to include derivatives of cyanoacetylene. The linear dication HCCCNH(2+) and its isomer HCCNCH(+2) are characterized in detail; according to CCSD(T)/6-31G(d,p)//MCSCF(7,13)/6-31G(d,p) estimates, HCCCNH(2+) is thermodynamically stable by 2.8 eV and the barrier to colinear dissociation is ca 4.1 eV. The isomer HCCNCH(2+) is thermodynamically stable by about 2.1 eV and the barrier to colinear dissociation is ca 4.5 eV. Preparation of these systems by charge stripping of the predecessor H2C3N monocation may be feasible. (C) 2009 Elsevier B.V. All rights reserved.Publication Open Access Dielectronic Recombination in He-like, Li-like and Be-like Yttrium and KLM Resonances(IOP PUBLISHING LTD, 2012-11-05) YUMAK YAHŞİ, AYŞE; Yumak, Ayse; Karakas, Vedat; Altun, Zikri; Williams, ID; VanDerHart, HW; McCann, JF; Crothers, DSFDR rate coefficients for He-like, Li-like and Be-like Yttrium ions and KLM resonances are calculated using MCBP approximation.Publication Metadata only Dielectronic recombination data for dynamic finite-density plasmas - VI. The boron isoelectronic sequence (vol 420, pg 775, 2004)(EDP SCIENCES S A, 2005) YUMAK YAHŞİ, AYŞE; Altun, Z; Yumak, A; Badnell, NR; Colgan, J; Pindzola, MS