Investigating Matter with Nucleonic Degrees of Freedom

At atomic levels, the chemical properties of matter are governed predominantly by the electromagnetic interactions. At smaller scales, two extra interactions – the strong and the weak forces – have also their say in dictating what properties the atomic nuclei should possess. For instance, the mass of all visible matter stems mainly from the mechanisms of the strong interaction giving rise to nucleons, or in general, hadrons. Another example concerns nuclear reactions which play crucial roles in probing the matter deep at the heart of the nucleus or right at its surface, allowing us to unravel the bulk and surface properties. The latter concerns nuclear structure and nuclear astrophysics and aims to address questions like "how could a small nucleus like Lithium made of three protons masquerade as a large one like Bismuth which constitutes 83 protons?" or "how can the bulk and surface properties of the stars' constituent nuclei determine the shape, mass, origin, and fate of the stars and neutron stars in the cosmos?"

The objectives of the Nuclear Physics group at Shiraz University root one way or another in our aspirations to understand the properties of matter on the scale of nuclei and nucleons, being the core constituents of natural and artificial elements. Specifically, the following research programs at Masters, PhD and postdoc (Dr. Ghahramany) levels constitute some of the analytical and experimental activities in our research group:

• How to find magnetic dipole moment of light nuclei using nuclear quarks model.
• Nondynamical spin polarization analysis of hadron-hadron elastic scattering at available energy.
• Hadron structure function determination using lepton deep.
• Industrial applications of positron lifetime spectroscopy (PLS) for detection of material and nano-material defects.
• Investigation of the effects of neutron and gamma irradiations on structure of nanoparticles using PLS.
• Study of thermal phase transition in nuclei as mesoscopic systems.
• Simulations and data analysis for nuclear structure studies of (or representative of) experiments of national and international stature.
• Analyzing different aspects of particle-matter interactions for medical physics applications.
• Studying various effects of ionizing radiations on biological microstructures.

Nader Ghahramany 's research area covers particle and nuclear physics, particularly, the interface between particle and nuclear physics. He has developed the quark-like nuclear model from which not only all existing magic numbers are obtained from quark statistic, also new magic number, 184 was derived for the first time in 2007. Using this model, more simple and accurate formula was derived for nuclear stability, binding energy, magnetic dipole moments and other nuclear processes such as alpha, beta, gamma decays and recently on nuclear internal conversion. His published papers also include investigation of hadronic interactions and calculation of structure functions and form factors of elastic and inelastic particle scatterings and also leptonic and semileptonic interactions by using QCD sum rules.

Zohreh Kargar's interests are experimental as well as theoretical nuclear physics. Her theoretical research interests have focused on investigation of nuclear level density and thermal phase transition in nuclei based on the mean BCS formalism [J. Phys. G 40(2013) 045108] and is currently working on clustering structure in nuclei [Nucl. Phys. A, Vol. 1015 ( 2021)122314]. The results are important for understanding nuclear structure and reactions which continue to be major goals in nuclear science and technology. Her experimental interest is applying positron lifetime spectroscopy (PLS) in studying defects in nanomaterials.

Hossein Moeini is interested in data analysis and simulations for nuclear structure and medical physics – investigating the physical and chemical effects of ionizing radiations on biological microstructures. Graduated in nuclear physics from the University of Groningen, he has performed proof-of-concept studies for the first feasibility experiment for EXL (Exotic nuclei studied in Light-ion induced reactions) at GSI Helmholtzzentrum für Schwerionenforschung. His experience as a researcher included the design and performance optimization of the electromagnetic calorimeter of the PANDA (Antiproton ANnihilation at DArmstadt) detector by analyzing a charmonium multi-photon decay channel, demonstrating that the calorimeter would meet the physics requirements for potential discoveries.

Nuclear Physics Laboratory

Quality control, detection and measurement of defects are important stages in the production of any product. A non-destructive test to evaluate the quality of products is positron lifetime spectroscopy (PLS). This method can be used for various materials, including metals, semiconductors, ceramic and polymer materials, both in the form of bulk and in the case of nanoparticles and nanopowders. Since the thermal propagation length of the positron is about a few nanometers, it is possible to detect nanoscale defects such as nanoscale holes. The lifetime of positron annihilation by electron depends on the electron density of defects, as such this subatomic particle has been used as a defect seeker particle.

In the research conducted in the nuclear laboratory of the physics department, the positron annihilation lifetime spectrometer was set up with a time resolution of 250 picoseconds. We have measured the amount of holes in the magnetic nanopowders of nickel ferrite and nickel ferrite substituted with copper. For this purpose, first these nanopowders were synthesized with the help of sol-gel method and then, using the positron annihilation spectroscopy method, the type and density of holes in these two types of powders were determined and measured. Also, the effect of hole density on the magnetic properties of the mentioned nanopowders was evaluated. The first news report in the monthly magazine of Nano Technology No. 241. The so-far published results of our research on developing the experimental program using PLS technique are

• "Positron annihilation and magnetic properties studies of copper substituted nickel ferrite nanoparticles", Nucl Instrum Methods Phys Res B, Vol. 375 (2016) 71-78.
• "Investigation of cation vacancies in Zinc substituted maghemite by positron lifetime and Doppler broadening spectroscopy", Appl. Radiat and Isotopes, 125 (2017) 18–22.
• "Positron annihilation lifetime, cation distribution and magnetic features of Ni1_xZnxFe2_xCoxO4 ferrite nanoparticles", RSC Adv.7 )2017( 22320-22328.
• "Investigation of positron annihilation lifetime and magnetic properties of Co1-xCuxFe2O4 nanoparticles", MRX, 6 (2018)15-23.
• "Positron Annihilation Lifetime Spectroscopy in Nickel Ferrite and Iron Oxide Nanopowders", Iranian Journal of Physics Research, Vol. 19, No. 2 (2019) 291-301.
• "Irradiation of Ni-Cu ferrite nanoparticles by 241Am-9Be source and investigation of their structural and magnetic properties using positron annihilation spectroscopy", Nucl Instrum Methods Phys Res B, Vol. 503 (2021) 37-44.
• "The use of positron lifetime spectroscopy (PLS) and X-ray diffraction (XRD) as measurement tools in investigating the effect of fast neutron radiation on the structural characteristics of nickel ferrite nanopowders", J. of New Approaches in Iranian Scientific Laboratories Vol. 5, No. 2 (2021) 41-49.

Please, do not hesitate to contact:

Assistant Professor Zohreh Kargar kargar@shirazu.ac.ir