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p-capture reaction cycles in rotating massive stars and their impact on elemental abundances in globular cluster stars: A case study of O, Na and Al

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Research in Astronomy and Astrophysics 2017年第8期17卷 31-46页

作者： Upakul Mahanta aruna goswami Hiralal Duorah Kalpana Duorah Department of Physics Bajali CollegePathsalaPIN 781325India Indian Institute of Astrophysics BengaluruPIN 560034India Department of Physics Gauhati UniversityGuwahatiPIN 781014India

Elemental abundance patterns of globular cluster stars can provide important clues for understanding cluster formation and early chemical *** origin of the abundance patterns,however,still remains poorly *** have studied the impact of p-capture reaction cycles on the abundances of oxygen,sodium and aluminium considering nuclear reaction cycles of carbon-nitrogenoxygen-fluorine,neon-sodium and magnesium-aluminium in massive stars in stellar conditions of temperature range 2×107to 10×107K and typical density of 102gm *** have estimated abundances of oxygen,sodium and aluminium with respect to Fe,which are then assumed to be ejected from those stars because of rotation reaching a critical *** ejected abundances of elements are then compared with their counterparts that have been observed in some metal-poor evolved stars,mainly giants and red giants,of globular clusters M3,M4,M13 and NGC *** observe an excellent agreement with[O/Fe]between the estimated and observed abundance values for globular clusters M3 and M4 with a correlation coefficient above 0.9 and a strong linear correlation for the remaining two clusters with a correlation coefficient above *** estimated[Na/Fe]is found to have a correlation coefficient above 0.7,thus implying a strong correlation for all four globular *** far as[Al/Fe]is concerned,it also shows a strong correlation between the estimated abundance and the observed abundance for globular clusters M13 and NGC 6752,since here also the correlation coefficient is above 0.7 whereas for globular cluster M4 there is a moderate correlation found with a correlation coefficient above *** sources of these discrepancies are discussed.

关键词： Galaxy globular cluster individual(M3,M4,M13,NGC 6752)—stars abundances—stars massive

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Effect of nitrogen doping on structural and optical properties of ZnO nanoparticles

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Progress in Natural Science:Materials International 2015年第4期25卷 300-309页

作者： Renu Kumari Anshuman Sahai Navendu goswami Inter University Accelerator Centre Aruna Asaf Ali Marg Department of Physics and Materials Science and Engineering Jaypee Institute of Information Technology

Infl uence of nitrogen doping on structural and optical properties of ZnO nanoparticles has been studied. Undoped and N doped ZnO nanoparticles were synthesized via chemical precipitation approach. The prepared samples were characterized through X-ray diffraction(XRD),Transmission electron microscopy(TEM) equipped with Energy dispersive X-ray(EDAX) spectroscopy, UV–visible spectroscopy, Fourier transform infrared(FTIR) spectroscopy and micro-Raman spectroscopy(m RS). Wurtzite phase of undoped as well as 0.5–10% N doped ZnO nanoparticles was con fi rmed through characteristic XRD patterns. The particle size expansion due to N incorporation in ZnO was further revealed by TEM and EDAX analysis where 11 nm size undoped and 18–22 nm size 0.5–10% N doped ZnO(N:ZnO) nanoparticles without any impurity were ascertained. Slight blue-shift in band gap energy, as observed in our case, symbolized weak quantum con fi nement of the prepared nanoparticles. The alterations in vibrational modes of ZnO due to N incorporation, remarkably H substituting at O site and subsequently causing the passivation in N:ZnO nanoparticles, were detected through FTIR analysis. Finally, the effect of the nano-size of crystallite and gradual prominence of N into ZnO lattice due to increase of N doping concentration in prepared nanoparticles was meticulously expatiated though m RS analysis.

关键词： II–VI Semiconductors Infrared spectra Raman spectra Optical properties of low-dimensional Mesoscopic Nanoscale materials and structures

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