Structure of the Lightest Tin Isotopes

We link the structure of nuclei around 100Sn, the heaviest doubly magic nucleus with equal neutron and proton numbers (N=Z=50), to nucleon-nucleon (NN) and three-nucleon (NNN) forces constrained by data of few-nucleon systems. Our results indicate that 100Sn is doubly magic, and we predict its quadrupole collectivity. We present precise computations of 101Sn based on three-particle–two-hole excitations of 100Sn, and we find that one interaction accurately reproduces the small splitting between the lowest Jπ=7/2+ and 5/2+ states.

PhysRevLett.120.152503.png

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Formation of Superheavy Elements in Nature

It is shown that superheavy elements may also be formed in the main r process responsible for the formation of the heaviest elements observed in nature. Under conditions of a high neutron density, the nucleosynthesis region lies close to the neutron drip line, so that the r process may circumvent the region where nuclei undergo spontaneous fissions and therefore have short lifetimes. However, a high induced-fission rate, which increases with the charge number, may prevent the nucleosynthesis wave from overcoming the region of isotopes heavier than curium, and the beta-decay chain leading to an increase in the charge number of product elements inevitably results in the spontaneous fission of the majority of product nuclei. Calculations of nucleosynthesis that were performed with available nuclear data within the scenario of a neutron-star merger reveal that only Z < 106 superheavy elements are formed. Their abundance at the end of the r process is commensurate with the abundance of uranium, but their lifetime does not exceed several years, so that they fast undergo decay.

 

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Micro-scale fusion in dense relativistic nanowire array plasmas

Nuclear fusion is regularly created in spherical plasma compressions driven by multi-kilojoule pulses from the world’s largest lasers. Here we demonstrate a dense fusion environment created by irradiating arrays of deuterated nanostructures with joule-level pulses from a compact ultrafast laser. The irradiation of ordered deuterated polyethylene nanowires arrays with femtosecond pulses of relativistic intensity creates ultra-high energy density plasmas in which deuterons (D) are accelerated up to MeV energies, efficiently driving D–D fusion reactions and ultrafast neutron bursts. We measure up to 2 × 106 fusion neutrons per joule, an increase of about 500 times with respect to flat solid targets, a record yield for joule-level lasers. Moreover, in accordance with simulation predictions, we observe a rapid increase in neutron yield with laser pulse energy. The results will impact nuclear science and high energy density research and can lead to bright ultrafast quasi-monoenergetic neutron point sources for imaging and materials studies.

Fig. 2

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QS rankings 2018 and the UoA Physics Department

The QS World University rankings for 2018 were announced very recently. It is always interesting to see some of the data regarding overall performance and assessment by the QS foundation. The latter uses their own algorithm and set of criteria to manage available bibliographical data (in collaboration with Elsevier as I read), thus producing a ranking list for several hundreds of universities around the World.

Regarding Physics I am interested in, our National and Kapodistrian University of Athens Physics Department is placed in positions 401-500, maintaining its status in the top-500 universities of the world. However, according to the QS criteria, UoA Physics is placed in the last position among Greek Physics Departments. See results and a screenshot below:

Putting aside the fact that NTUA (ranked in 151-200) is not a pure Physics Department, AUTh occupies the second place, while U.Crete is in No3.

Amid non-existent research funding, personnel reduction to a 40% with respect to what it was 3-4 years ago, turbulence with new legislation and “reforms”

I am personally very happy that NTUA Physics is still in the top-500. A different ranking based on another set of criteria (excluding from points the number of foreign students and faculty, mutlilingual programs, international character etc) has put the Physics Dept of UoA in the 101-150 worldwide for 2016 and 76-100 in 2017. Not bad for what we, as faculty, experience in our miserable everyday lifes.

Ανακοίνωση για Ατομική και Μοριακή Φυσική

Όσοι και όσες ενδιαφέρονται για το μάθημα “Ατομική και Μοριακή Φυσική” (επιλογής, εαρινό εξάμηνο 2017-18) παρακαλούνται να προσέλθουν σε μια πρώτη συνάντηση με τους διδάσκοντες για τον καθορισμό του ωρολόγιου προγράμματος διδασκαλίας.

Τετάρτη 14.02.2018 12’00 στην Αίθουσα “Ήρων”

 

Assistant Professor | Department of Physics | University of Athens