Chemistry for the r process

Lead Research Organisation: University of Surrey
Department Name: Physics


'How Do Nuclear Reactions Power Astrophysical Processes and Create the Chemical Elements?' is one of the big science questions. The most mysterious of the several process involved, it the rapid neutron capture process (r process). It is believed to synthetise half of the elements heavier than iron. Its understanding requires knowledge of the properties of nuclei involved and the conditions in the astrophysical site. Presently the favoured/possible astrophysical sites are neutron-star mergers and magneto-rotational supernovae explosions. The nuclei produced in such explosive scenarios are extremely neutron rich, very far from the line of stability. Consequently, the large majority of them were never synthetized on Earth, and the abundance calculations have to use nuclear properties obtained from theories. The abundance peak around mass number A~190 is the consequence of the N=126 magic neutron number. The study of the neutron-rich N=126 nuclei is a key aim of the leading nuclear physics facilities such as FAIR/GSI and CERN-ISOLDE etc.
Here, a novel detection system will be designed, based on simulations and available experimental information for the study of extremely neutron-rich nuclei produced in multi-nucleon transfer reactions. Identification and separation based on chemical methods, used for super-heavy elements will be merged with conventional nuclear physics techniques for the first time. This is a proof-of-concept study requiring multidisciplinary (physics and chemistry) approach. Its ultimate aim is to develop a project aimed at building a system to study the properties of neutron-rich nuclei on the r-process waiting path, therefore addressing the question of how and where heavy elements were/are formed in the universe.

Planned Impact

One of the big open science questions is 'how the chemical elements were made'. The first neutron-star mergers were observed in 2017. From the observation of how the remnant's optical spectrum changed over time from blue to red, it was inferred that heavy elements around Pt-Au were synthetized (but note, that actually no individual chemical elements were identified). All this attracted huge media interest. The same is true for the recent naming of the heaviest elements (up to element 118). Due to the link with nucleosynthesis, neutron-star mergers, gravitational waves, as well as the use of techniques developed for super-heavy elements, the present proposal has high potential for public engagement.
Also, it will develop skills, leadership and infrastructure.
For the final setup, the specialised Si detectors most likely will be produced in the UK.


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