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HomeSciencePhysicsHighest-Order Electromagnetic Transition Observed

Highest-Order Electromagnetic Transition Observed

• Physics 16, s47

Observations ship proof of an unique “sixth-order” electromagnetic transition within the gamma-ray emission of an iron isotope, a discovering that might present new methods to check nuclear fashions.

APS/Carin Cain

Much like an atom’s electrons, an atom’s nucleus can exist in floor and excited states. It may also emit photons—sometimes at gamma-ray wavelengths—because the nucleus transitions between these states. The most simply noticed of those transitions, that are categorized by their “multipolarity,” are the low-order ones (dipolar and quadrupolar), which may be modeled because the emission of oscillating dipoles or quadrupoles. As the order will increase, the transitions turn out to be much less possible—and their names extra intricate. Previously, the fifth-order transition (often called triacontadipole) was the highest-order transition noticed. Now Alan John (AJ) Mitchell of the Australian National University and colleagues have supplied conclusive proof for the sixth-order transition (hexacontatetrapole) [1].

Hints of the hexacontatetrapole transition first appeared in experiments within the Seventies on iron-53 (53Fe). Those experiments detected a faint 3041-keV photon emission that might not be ascribed to a lower-order transition. Those research, nonetheless, couldn’t rule out the chance that the weak sign got here from a summing artifact by which a number of low-energy photons concurrently hit the detector and get recorded as one high-energy photon.

To settle the problem, Mitchell and colleagues carried out high-precision gamma-ray spectroscopy experiments on excited 53Fe isomers produced at a heavy-ion accelerator. Feeding the info into simulations, they confirmed that summing supplied a negligible contribution to the 3041-keV line, establishing the sixth-order nature of the transition. The workforce additionally quantified the energy of this transition and improved the characterization of the strengths and energies of the fourth- and fifth-order transitions. Since these high-multipolarity transitions are essentially completely different from low-order ones, Mitchell says that “these data provide a unique way to test nuclear-shell models.”

–Matteo Rini

Matteo Rini is the Editor of Physics Magazine.


  1. T. Palazzo et al., “Direct measurement of hexacontatetrapole, E6 𝛾 decay from 53mFe,” Phys. Rev. Lett. 130, 122503 (2023).

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