[Triumf-seminars] TRIUMF Colloquium today at 14:00

[TRIUMF Seminars]

Date/Time: Thu 2021-12-09 at 14:00

Location:  Remote              

Speaker:   Kieran Flanagan (University of Manchester)

Title:     Shining light on magic nuclei

Abstract: A full understanding of the nucleus remains one of the great challenges of modern science. The goal of nuclear physics/theory is to simultaneously describe nuclei from light systems with just a few interacting nucleons, to heavy systems consisting of hundreds of nucleons occupying dimensions of just a few femtometers. The size of these systems is too large for a reductionist approach, yet is also too small for thermodynamic averaging to help. This is further complicated by the absence/lack of a full description of the nature of the interaction that glues nucleons together. 


Despite these complexities, regular predictable structure emerges. The most striking of these features are the magic numbers of protons and neutrons that mark regions of enhanced stability. The impact of a shell closure does not only influence the mass and lifetime of the state but other observables as well, including the distribution of charge and the nuclear shape. While early models assumed nuclei to be spherical, this assumption quickly proved insufficient, since only systems that have closed neutron and proton shells (doubly magic) are found to be spherical. The majority of nuclei have a deformed nature that results from correlated motion of many particles forming collective states. Determining the shape of a nucleus is therefore a very powerful way to study to what extent it can be considered magic, with a closed-shell structure. 


One method to determine nuclear shapes precisely measures the energy of electrons bound to the nucleus, using optical spectroscopy. Such measurements extract the nuclear moments and changes in mean square charge radius across an isotope chain. Through comparison with modern nuclear theory, current model assumptions associated with the underlying inter-nucleon forces can be stringently tested. In particular, recent mass and half-life measurements highlight dramatic changes in the structure of nuclei, pointing to new magic numbers emerging and existing ones disappearing as more neutrons are added to the nucleus. Over the last 10 years the CRIS collaboration at ISOLDE CERN has performed a series of laser spectroscopy experiments that have focused on understanding the evolution of the nuclear shape in exotic nuclei and the persistence of the magic numbers with neutron excess.  This talk will present the experimental developments and latest results that challenge the evolution of new magic numbers.

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https://ubc.zoom.us/j/69604219530?pwd=SWV0QVp1cGQ3OXlpOUNqa1hTOHY3Zz09 

Meeting ID: 696 0421 9530 
Passcode: 465904



remote

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