Exotic nuclear shapes with radioactive ion beams
Lead Research Organisation:
University of Liverpool
Department Name: Physics
Abstract
Atomic nuclei, made up of protons and neutrons, are fundamental building blocks of nature that have been known to exist for more than 100 years. Yet, the structure of the nucleus is not even close to being understood, either in terms of its collective behaviour or individual nucleon interactions. We most often picture atomic nuclei as a spherical ball at the centre of orbiting electrons, completing the textbook version of the atom. However, what we do know is that this complex quantum system of protons and neutrons at the centre is almost never spherical, but deformed. Nuclei have shapes, from rugby-balls (prolate) and Smarties (oblate) to pears (octupole).
Predicting shapes is difficult, and nuclear theory cannot always predict the exotic shape phenomena that arise in experimental discoveries. The shape turns out to be a very sensitive test of nuclear-structure models. Shape can help distinguish which models perform best, and which ones are most reliable at predicting experimental findings in the heaviest (and newest!) elements, for example.
The most interesting shapes are often to be found in radioactive isotopes with very short half-lives. These exotic nuclei can be studied though, at facilities such as ISOLDE at CERN. Here, high-energy and high-intensity proton beams bombard targets of materials such as uranium carbide, to produce almost a thousand different isotopes. These are then filtered by mass and element before being transported and accelerated to various experimental stations where they can be studied. In this research, the radioactive beams need to be energetic so that secondary reactions can be induced. This is done by re-accelerating the extracted isotopes to around 10% of the speed of light and focusing the beam onto thin foils of isotopically pure materials.
Nuclear shape is important not only for nuclear-structure physics, but also for the study of fundamental symmetries in physics. The understanding of pear-shaped nuclei has strong implications in the search for atomic electric dipole moments (EDMs), where the reflection-asymmetric charge distribution in the nucleus enhances the EDM. A non-zero EDM would imply a violation of the charge-parity symmetry (CP-violation) and herald a new era of testing physics beyond the current standard model. The race is on for such a discovery, particularly in the odd-mass radon and radium isotopes, which form part of this study. Indeed, understanding CP-violation is seen as a route to the understanding of the observed matter/anti-matter asymmetry in the early universe, which led to our existence today.
Predicting shapes is difficult, and nuclear theory cannot always predict the exotic shape phenomena that arise in experimental discoveries. The shape turns out to be a very sensitive test of nuclear-structure models. Shape can help distinguish which models perform best, and which ones are most reliable at predicting experimental findings in the heaviest (and newest!) elements, for example.
The most interesting shapes are often to be found in radioactive isotopes with very short half-lives. These exotic nuclei can be studied though, at facilities such as ISOLDE at CERN. Here, high-energy and high-intensity proton beams bombard targets of materials such as uranium carbide, to produce almost a thousand different isotopes. These are then filtered by mass and element before being transported and accelerated to various experimental stations where they can be studied. In this research, the radioactive beams need to be energetic so that secondary reactions can be induced. This is done by re-accelerating the extracted isotopes to around 10% of the speed of light and focusing the beam onto thin foils of isotopically pure materials.
Nuclear shape is important not only for nuclear-structure physics, but also for the study of fundamental symmetries in physics. The understanding of pear-shaped nuclei has strong implications in the search for atomic electric dipole moments (EDMs), where the reflection-asymmetric charge distribution in the nucleus enhances the EDM. A non-zero EDM would imply a violation of the charge-parity symmetry (CP-violation) and herald a new era of testing physics beyond the current standard model. The race is on for such a discovery, particularly in the odd-mass radon and radium isotopes, which form part of this study. Indeed, understanding CP-violation is seen as a route to the understanding of the observed matter/anti-matter asymmetry in the early universe, which led to our existence today.
People |
ORCID iD |
Liam Gaffney (Principal Investigator / Fellow) |
Publications
Barzakh A
(2021)
Large Shape Staggering in Neutron-Deficient Bi Isotopes.
in Physical review letters
Barzakh A
(2022)
Producing gold at ISOLDE-CERN
in Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Bennett S
(2023)
Direct Determination of Fission-Barrier Heights Using Light-Ion Transfer in Inverse Kinematics
in Physical Review Letters
Butler PA
(2019)
The observation of vibrating pear-shapes in radon nuclei.
in Nature communications
Butler PA
(2020)
Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive ^{222}Ra and ^{228}Ra Beams.
in Physical review letters
Butler PA
(2020)
Addendum: The observation of vibrating pear-shapes in radon nuclei.
in Nature communications
Butler PA
(2020)
Publisher Correction: The observation of vibrating pear-shapes in radon nuclei.
in Nature communications
Day Goodacre T
(2021)
Charge radii, moments, and masses of mercury isotopes across the N = 126 shell closure
in Physical Review C
Harding R
(2021)
Laser-assisted nuclear decay spectroscopy of Au 176 , 177 , 179
in Physical Review C
Kern R
(2020)
Restoring the valence-shell stabilization in Nd 140
in Physical Review C
Description | A flexible open-access wire bonder for the ISOLDE Solenoidal Spectrometer upgrade project |
Amount | £72,993 (GBP) |
Funding ID | ST/W005670/1 |
Organisation | Science and Technologies Facilities Council (STFC) |
Sector | Public |
Country | United Kingdom |
Start | 12/2021 |
End | 03/2022 |
Title | ISOLDE Solenoidal Spectrometer Sort Code |
Description | A code to read and process the raw data from the ISOLDE Solenoidal Spectrometer experiment at CERN. It builds physics events and performs correlations, producing a range of histograms for the user. |
Type Of Material | Data analysis technique |
Year Produced | 2021 |
Provided To Others? | Yes |
Impact | First experiments of ISOLDE Solenoidal Spectrometer use this code for the online data viewing and offline analysis. |
URL | https://github.com/ISOLDESolenoidalSpectrometer/ISSSort |
Title | Miniball Sort Code |
Description | A data sorting and analysis code for Miniball experiments at ISOLDE. This code is designed to take the raw data files from the experiment and convert them to ROOT trees, then subsequently analyse them to produce particle-gated, Doppler corrected gamma-ray spectra for analysis. |
Type Of Material | Data handling & control |
Year Produced | 2018 |
Provided To Others? | Yes |
Impact | This software is continually developed by myself by use for the whole collaboration, including our recent publications in Nature Communications and Physical Review Letters. The latest release should allow all experiments from 2017 and 2018, performed with Miniball to reach the publication-quality stage. |
URL | https://github.com/Miniball/MiniballCoulexSort |
Title | Miniball Sort Code for new FEBEX DAQ |
Description | A code to process the raw data from the new Miniball FEBEX DAQ and build time correlated events. In the end it also produces a range of physics histograms for the user to do the analysis. |
Type Of Material | Data analysis technique |
Year Produced | 2022 |
Provided To Others? | Yes |
Impact | First test data of the new Miniball DAQ is being processed and visualised with this code. |
URL | https://github.com/Miniball/MiniballSort |
Title | chisqsurface code for Gosia |
Description | A technique and associated computer code for analysing a multi-dimensional chisq-surface originating from Coulomb-excitation experiments. The code uses the existing Gosia fortran code for Coulomb-excitation analysis and interfaces this with a C++ wrapper to handle the input files and produce the resulting surface in ROOT format. |
Type Of Material | Data analysis technique |
Year Produced | 2014 |
Provided To Others? | Yes |
Impact | Multiple papers using results generated from this code, including on-going analysis. It was originally designed for experiments from ISOLDE, but has now been expanded over time to be more and more generic allowing a wider user base. |
URL | https://github.com/lpgaff/chisqsurface |
Title | Miniball Sort Code |
Description | A data sorting and analysis code for Miniball experiments at ISOLDE. This code is designed to take the raw data files from the experiment and convert them to ROOT trees, then subsequently analyse them to produce particle-gated, Doppler corrected gamma-ray spectra for analysis. |
Type Of Technology | Software |
Year Produced | 2019 |
Impact | This software is continually developed by myself by use for the whole collaboration, including our recent publication in Nature Communications. The latest release should allow all experiments from 2017 and 2018, performed with Miniball to reach the publication-quality stage. |
URL | https://github.com/Miniball/MiniballCoulexSort |
Description | Binding Blocks Summer Masterclass Webinar |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Schools |
Results and Impact | A webinar about experimental nuclear physics and studying exotic isotopes at the summer masterclass with the Binding Blocks team |
Year(s) Of Engagement Activity | 2022 |
URL | https://sites.google.com/york.ac.uk/bindingblocks/pre-16/ |
Description | Binding Blocks Winter Masterclass Webinar |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Schools |
Results and Impact | A webinar about experimental nuclear physics and studying exotic isotopes at the winter masterclass with the Binding Blocks team |
Year(s) Of Engagement Activity | 2022 |
URL | https://sites.google.com/york.ac.uk/bindingblocks/post-16/webinars-winter-202223 |
Description | I'm a Scientist, Get Me Out Of Here (CERN Zone) |
Form Of Engagement Activity | Engagement focused website, blog or social media channel |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Schools |
Results and Impact | I am leader of the ISOLDE Team in the CERN Zone of I'm A Scientist Get Me Out Of Here, which directly engages Y10-13 students in online chats, Q&A forums, laboratory updates/tours, etc. |
Year(s) Of Engagement Activity | 2022,2023 |
URL | https://cern22.imascientist.org.uk/team/isolde |
Description | I'm a Scientist, Get Me Out Of Here (November 2019) |
Form Of Engagement Activity | Engagement focused website, blog or social media channel |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Schools |
Results and Impact | A two-week long event engaging with school classes in an online chatroom. Scientists were asked questions inside and outside of the chatroom giving the chance for school students to engage and understand/normalise science. It was really successful and the reports back from the schools involved were very positive on the impact it had for the students. One class also plans to visit CERN in the summer and I will meet them there to give them an extra tour of the ISOLDE facility. |
Year(s) Of Engagement Activity | 2019 |
URL | https://about.imascientist.org.uk/2020/nuclear-zone-report-november-2019/ |
Description | Pizza night at University of Liverpool |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Undergraduate students |
Results and Impact | A talk to around 20 final-year undergraduate students about my research projects. The evening was catered with Pizza on behalf of the student office at the department of physics and the engagement was very positive. Around half the students stayed on after the talk to ask further questions and discuss options for PhD opportunities. |
Year(s) Of Engagement Activity | 2020 |
Description | Pizza night at the University of Liverpool |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Undergraduate students |
Results and Impact | A talk to 6 final-year undergraduate students about my research projects. The evening took place on Zoom due to the pandemic, which would usually have encouraged participation by offering free pizza. |
Year(s) Of Engagement Activity | 2020 |