Nuclear structure in extremely exotic systems explored by laser spectroscopy of pure ion beams.
Lead Research Organisation:
University of Liverpool
Department Name: Physics
Abstract
Atomic nuclei form the fundamental building blocks for most of what we see around us. Understanding the quantum arrangement of protons and neutrons within the nucleus, their stability, the nature of the forces which hold them together and even how the elements were formed in the universe are the subject of nuclear structure research. Surrounding the nucleus, orbiting electrons occupy quantum 'shelves' at discrete energies, with an arrangement largely dependent upon the proton number (ie. element) under study. However, on a hyperfine level, these energy levels move and split as a result of changing nuclear properties such as size, shape, magnetization and quantum spin as neutrons are added to create different isotopes. Precision lasers can be used to excite electrons between these levels to reveal such properties. To more fully understand the nature of the nuclear forces we need to know how nuclear properties change for exotic nuclei with unnatural combinations of proton and neutron numbers (Z and N). Such nuclei may live for less than a millisecond. Produced with a distribution in N and Z from nuclear reactions at 'isotope factories', they are electrostatically transported as a beam of ions to a station for spectroscopy. A specific mass (N+Z) is selected using in-flight magnetic deflection, but how can we choose a single element? The isotope (N,Z) we wish to study may be a part per million of the total beam selected by mass only. A few sheep would be hard to see in a field of a million goats. New international facilities aim to produce more, but will not fulfill their potential if they produce more of both. This is a long standing problem in nuclear physics research. To a laser beam, quantum electron levels provide a fingerprint for each element. At a characteristic frequency of light, the electrons are excited between levels in one element alone. Moreover, a combination of laser beams and excitation steps will remove an additional electron altogether. A bunch of ions (released from a trap, with ample time to interact with the laser) with two electrons removed from their neutral atomic state rather than one, and therefore twice the charge, will travel to the spectroscopy station faster under electrostatic acceleration. Arriving earlier, only nuclei of a single N and Z will be present, and other combinations (all arriving later) kicked away. Using a laser to study (as well as purify) the beam of nuclei reveals all the properties above by detecting photons emitted by electrons relaxing back after excitation as a function of frequency. Purification will allow lasers to study nuclei which are produced at a rate of less than one per second (compared with 1000/s required today), and irrespective of what other elements with isotopes of the same mass are present. Within the nucleus, neutrons and protons each occupy their own quantum shelves, lying at discrete energies. These are filled sequentially, and the interaction between nucleons raises or lowers their energy as the levels are filled. Level migrations, the consequent changes to the energy gaps between them or even a reordering, fundamentally affect the nuclear properties. These measurements will provide a sensitive probe of species far from stability in order to understand nuclear interactions. Lying at the corner stone of the natural (and unnatural) world nuclear science finds applications beyond its chapter. It has long been suspected that thorium-229 contains an isomer - that is, a nuclear state excited in energy which lives at least momentarily. If observed, this would have the lowest energy of any seen in nature and could be the first demonstration of nuclear excitation with a laser. Considerable interest has been gathered to use the isomer as an accurate clock (from an oscillating nuclear transition), testing Einstein's theory of relativity and how constant the fundamental physical constants really are - one of the greatest unanswered problems in physics.
Organisations
- University of Liverpool (Fellow, Lead Research Organisation)
- Technical University of Darmstadt (Collaboration)
- University of Manchester (Collaboration)
- Heidelberg University (Collaboration)
- McGill University (Collaboration)
- TRIUMF (Collaboration)
- Université Catholique de Louvain (Collaboration)
- University of Leuven (Collaboration)
- Helmholtz Association of German Research Centres (Collaboration)
- University of Jyväskylä (Collaboration)
- Johannes Gutenberg University of Mainz (Collaboration)
- European Organization for Nuclear Research (CERN) (Collaboration)
People |
ORCID iD |
Bradley Cheal (Principal Investigator / Fellow) |
Publications
Yordanov DT
(2016)
Simple Nuclear Structure in (111-129)Cd from Atomic Isomer Shifts.
in Physical review letters
Yang XF
(2016)
Isomer Shift and Magnetic Moment of the Long-Lived 1/2^{+} Isomer in _{30}^{79}Zn_{49}: Signature of Shape Coexistence near ^{78}Ni.
in Physical review letters
Yang X
(2018)
Investigating the large deformation of the 5 / 2 + isomeric state in Zn 73 : An indicator for triaxiality
in Physical Review C
Wraith C
(2017)
Evolution of nuclear structure in neutron-rich odd-Zn isotopes and isomers
in Physics Letters B
Wraith C
(2017)
Evolution of nuclear structure in neutron-rich odd-Zn isotopes and isomers
in Physics Letters B
Voss A
(2017)
High-resolution laser spectroscopy of long-lived plutonium isotopes
in Physical Review A
Voss A
(2015)
Nuclear moments and charge radii of neutron-deficient francium isotopes and isomers
in Physical Review C
Voss A
(2013)
First Use of High-Frequency Intensity Modulation of Narrow-Linewidth Laser Light and Its Application in Determination of Fr 206 , 205 , 204 Ground-State Properties
in Physical Review Letters
Vormawah L
(2018)
Isotope shifts from collinear laser spectroscopy of doubly charged yttrium isotopes
in Physical Review A
Procter T
(2015)
Direct observation of an isomeric state in 98Rb and nuclear properties of exotic rubidium isotopes measured by laser spectroscopy
in The European Physical Journal A
Neugart R
(2017)
Collinear laser spectroscopy at ISOLDE: new methods and highlights
in Journal of Physics G: Nuclear and Particle Physics
Lautenschläger F
(2016)
Developments for resonance ionization laser spectroscopy of the heaviest elements at SHIP
in Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Laatiaoui M
(2016)
Atom-at-a-time laser resonance ionization spectroscopy of nobelium.
in Nature
Heylen H
(2016)
Changes in nuclear structure along the Mn isotopic chain studied via charge radii
in Physical Review C
Heylen H
(2015)
Spins and magnetic moments of Mn 58 , 60 , 62 , 64 ground states and isomers
in Physical Review C
Hammen M
(2018)
From Calcium to Cadmium: Testing the Pairing Functional through Charge Radii Measurements of ^{100-130}Cd.
in Physical review letters
Frömmgen N
(2015)
Collinear laser spectroscopy of atomic cadmium Extraction of nuclear magnetic dipole and electric quadrupole moments
in The European Physical Journal D
Chhetri P
(2017)
Impact of buffer gas quenching on the 1S0 ? 1P1 ground-state atomic transition in nobelium
in The European Physical Journal D
Cheal B
(2015)
Recent Advances in On-Line Laser Spectroscopy
in Nuclear Physics News
Bissell M
(2016)
Cu charge radii reveal a weak sub-shell effect at N = 40
in Physical Review C
Babcock C
(2016)
Quadrupole moments of odd-A 53-63 Mn: Onset of collectivity towards N = 40
in Physics Letters B
Babcock C
(2015)
Evidence for Increased neutron and proton excitations between 51-63 Mn
in Physics Letters B
Description | Established a method of moving atomic electrons into different energy levels in an ion trap, so that high resolution laser spectroscopy can be performed more efficiently, and with greater sensitivity to properties of nuclei. This has been used at the radioactive nuclear facility at ISOLDE, CERN, initially in the study of deformation in neutron-rich manganese isotopes. Additionally, at a complementary accelerator facility at JYFL, Finland, the experimental layout has been optimised to allow this to happen, and been applied to the studies of scandium and yttrium isotopes. |
Exploitation Route | Used for efficient and effective laser spectroscopy, which is an invaluable tool in the determination of properties of nuclear ground and isomeric states. |
Sectors | Other |
Description | COLLAPS, ISOLDE Laser Spectroscopy |
Organisation | Catholic University of Louvain |
Country | Belgium |
Sector | Academic/University |
PI Contribution | Proposal and running of experiments. Contribution to equipment and consumables costs. |
Collaborator Contribution | Provision of laboratory apparatus and expertise. |
Impact | Active experiments directly related to the research proposal have been approved by the local Programme Advisory Committee. The experimental apparatus required and accelerator beam time have been made available. Several publications have been published or are in preparation. |
Start Year | 2013 |
Description | COLLAPS, ISOLDE Laser Spectroscopy |
Organisation | European Organization for Nuclear Research (CERN) |
Department | CERN - ISOLDE |
Country | Switzerland |
Sector | Academic/University |
PI Contribution | Proposal and running of experiments. Contribution to equipment and consumables costs. |
Collaborator Contribution | Provision of laboratory apparatus and expertise. |
Impact | Active experiments directly related to the research proposal have been approved by the local Programme Advisory Committee. The experimental apparatus required and accelerator beam time have been made available. Several publications have been published or are in preparation. |
Start Year | 2013 |
Description | COLLAPS, ISOLDE Laser Spectroscopy |
Organisation | Heidelberg University |
Country | Germany |
Sector | Academic/University |
PI Contribution | Proposal and running of experiments. Contribution to equipment and consumables costs. |
Collaborator Contribution | Provision of laboratory apparatus and expertise. |
Impact | Active experiments directly related to the research proposal have been approved by the local Programme Advisory Committee. The experimental apparatus required and accelerator beam time have been made available. Several publications have been published or are in preparation. |
Start Year | 2013 |
Description | COLLAPS, ISOLDE Laser Spectroscopy |
Organisation | Technical University of Darmstadt |
Country | Germany |
Sector | Academic/University |
PI Contribution | Proposal and running of experiments. Contribution to equipment and consumables costs. |
Collaborator Contribution | Provision of laboratory apparatus and expertise. |
Impact | Active experiments directly related to the research proposal have been approved by the local Programme Advisory Committee. The experimental apparatus required and accelerator beam time have been made available. Several publications have been published or are in preparation. |
Start Year | 2013 |
Description | GSI Laser Spectroscopy |
Organisation | Helmholtz Association of German Research Centres |
Department | GSI Helmholtz Centre for Heavy Ion Research |
Country | Germany |
Sector | Public |
PI Contribution | Assist in set-up and running of experiments. Co-spokesperson of proposal (ENSAR coordinator). |
Collaborator Contribution | Equipment, facility and expertise. |
Impact | At least two publications currently in press. First measurement of an optical resonance in nobelium. |
Start Year | 2014 |
Description | GSI Laser Spectroscopy |
Organisation | Helmholtz Association of German Research Centres |
Department | Helmholtz Institute Mainz |
Country | Germany |
Sector | Academic/University |
PI Contribution | Assist in set-up and running of experiments. Co-spokesperson of proposal (ENSAR coordinator). |
Collaborator Contribution | Equipment, facility and expertise. |
Impact | At least two publications currently in press. First measurement of an optical resonance in nobelium. |
Start Year | 2014 |
Description | GSI Laser Spectroscopy |
Organisation | Johannes Gutenberg University of Mainz |
Country | Germany |
Sector | Academic/University |
PI Contribution | Assist in set-up and running of experiments. Co-spokesperson of proposal (ENSAR coordinator). |
Collaborator Contribution | Equipment, facility and expertise. |
Impact | At least two publications currently in press. First measurement of an optical resonance in nobelium. |
Start Year | 2014 |
Description | GSI Laser Spectroscopy |
Organisation | Technical University of Darmstadt |
Country | Germany |
Sector | Academic/University |
PI Contribution | Assist in set-up and running of experiments. Co-spokesperson of proposal (ENSAR coordinator). |
Collaborator Contribution | Equipment, facility and expertise. |
Impact | At least two publications currently in press. First measurement of an optical resonance in nobelium. |
Start Year | 2014 |
Description | GSI Laser Spectroscopy |
Organisation | University of Leuven |
Country | Belgium |
Sector | Academic/University |
PI Contribution | Assist in set-up and running of experiments. Co-spokesperson of proposal (ENSAR coordinator). |
Collaborator Contribution | Equipment, facility and expertise. |
Impact | At least two publications currently in press. First measurement of an optical resonance in nobelium. |
Start Year | 2014 |
Description | JYFL Laser Spectroscopy |
Organisation | University of Jyvaskyla |
Country | Finland |
Sector | Academic/University |
PI Contribution | Running of the laser spectroscopy set-up, contribution to equipment/consumable funding, spokesperson of several experiments. |
Collaborator Contribution | Provision of laboratory space, equipment and accelerator use. |
Impact | Active experimental proposals have been awarded accelerator beam time by the local Programme Advisory Committee. The experimental apparatus required to carry out the research has now been commissioned. Many publications in progress. |
Start Year | 2013 |
Description | JYFL Laser Spectroscopy |
Organisation | University of Manchester |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Running of the laser spectroscopy set-up, contribution to equipment/consumable funding, spokesperson of several experiments. |
Collaborator Contribution | Provision of laboratory space, equipment and accelerator use. |
Impact | Active experimental proposals have been awarded accelerator beam time by the local Programme Advisory Committee. The experimental apparatus required to carry out the research has now been commissioned. Many publications in progress. |
Start Year | 2013 |
Description | TRIUMF Laser Spectroscopy |
Organisation | McGill University |
Country | Canada |
Sector | Academic/University |
PI Contribution | Proposal and running of experiments. Contribution to equipment and consumables. |
Collaborator Contribution | Provision of laboratory space, apparatus and experience. |
Impact | Active experiments directly related to the research proposal have been approved by the local Programme Advisory Committee. The experimental apparatus required and accelerator beam time have been made available. |
Start Year | 2013 |
Description | TRIUMF Laser Spectroscopy |
Organisation | TRIUMF |
Country | Canada |
Sector | Academic/University |
PI Contribution | Proposal and running of experiments. Contribution to equipment and consumables. |
Collaborator Contribution | Provision of laboratory space, apparatus and experience. |
Impact | Active experiments directly related to the research proposal have been approved by the local Programme Advisory Committee. The experimental apparatus required and accelerator beam time have been made available. |
Start Year | 2013 |