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Collective 2+1 excitations in 206Po and 208,210Rn
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Authors
- T. Grahn
- J. Pakarinen
- L. Jokiniemi
- M. Albers
- K. Auranen
- C. Bauer
- C. Bernards
- A. Blazhev
- P. A. Butler
- S. Bönig
- A. Damyanova
- T. De Coster
- H. De Witte
- J. Elseviers
- L. P. Gaffney
- M. Huyse
- A. Herzáň
- U. Jakobsson
- R. Julin
- N. Kesteloot
- J. Konki
- Th. Kröll
- L. Lewandowski
- K. Moschner
- P. Peura
- M. Pfeiffer
- D. Radeck
- P. Rahkila
- E. Rapisarda
- P. Reiter
- K. Reynders
- M. Rudiger
- M. -D. Salsac
- S. Sambi
- M. Scheck
- M. Seidlitz
- B. Siebeck
- T. Steinbach
- S. Stolze
- J. Suhonen
- P. Thoele
- M. Thürauf
- N. Warr
- P. Van Duppen
- M. Venhart
- M. J. Vermeulen
- V. Werner
- M. Veselsky
- A. Vogt
- K. Wrzosek-Lipska
- M. Zielińska
What were we trying to understand?
We studied how certain heavy atomic nuclei behave when they are excited — specifically nuclei of polonium (²⁰⁶Po) and radon (²⁰⁸Rn and ²¹⁰Rn). In very simple terms, we wanted to know whether the protons and neutrons inside these nuclei act largely independently, or whether they move together in a coordinated way. This kind of coordinated motion — where many particles inside a nucleus participate collectively in an excitation — tells us about the fundamental structure of the nucleus and how nuclear forces shape it.
How did we investigate this?
We used an experimental technique called Coulomb excitation, in which a fast beam of radioactive nuclei is directed at a target and gently “shaken” by electromagnetic forces — like nudging a bell to make it ring without touching it directly. From the resulting gamma-ray emissions, we can extract a quantity called the B(E2) value for the transition from the first excited state (called 2⁺₁) down to the ground state (0⁺₁). A larger B(E2) value signals stronger collective motion of protons and neutrons in the nucleus.
To do this, we accelerated beams of these exotic nuclei at the CERN-ISOLDE facility and detected the gamma rays they emitted after being excited — a technically demanding measurement involving radioactive ion beams and precision detectors.
What did we learn and why does it matter?
We found that the B(E2) values in ²⁰⁶Po and ²⁰⁸,²¹⁰Rn are higher than expected if the nucleons were behaving independently (as simple shell models would predict). This tells us that collective effects — where many nucleons move in a coordinated fashion — are present even near the classical “magic numbers” of protons and neutrons that usually stabilize independent motion. In particular, moving away from the neutron number N = 126 closed shell, the nuclei start showing enhanced collectivity in their first excited states.
Why is this important? These results help refine our understanding of how nuclear structure evolves in heavy, neutron-deficient isotopes. They provide input for nuclear models that are used across physics — from interpreting astrophysical nucleosynthesis to improving nuclear technologies and fundamental tests of the strong force in matter.
Journal info
Article type: Regular Article
Impact factor: 3.131
ISSN: 14346001
The European Physical Journal A (EPJ A) presents new and original research results in Hadron physics and Nuclear physics.
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