The gamma-ray emission of an iron isotope shows signs of an unusual "sixth order" electromagnetic transition that could open new avenues for nuclear model testing.
The ground and excited states of an atom's nucleus are similar to those of the atom's electrons. The nucleus can also emit photons, usually at gamma-ray wavelengths, as it changes between different states. Low-order transitions (dipolar and quadrupolar), which can be defined as the emission of oscillating dipoles or quadrupoles, are the easiest to see among these transitions, categorized by their "multipolarity". The higher the rank, the less likely transitions become and their names become more complex. The highest-order transition ever recorded was the fifth-order transition, also known as triacontadipole.
Recently, Alan John (AJ) Mitchell of the Australian National University and colleagues presented convincing evidence for sixth-degree transition. (hexacontatetrapole).
In tests on iron-1970 in the 53s, the hexacontatetrapol transition showed signs of occurrence for the first time. (53Fe). These tests detected a weak photon emission at 3041 keV that was not caused by a lower-order transition. However, these investigations could not rule out the possibility that the weak signal was caused by a summation artifact, in which a series of low-energy photons hit the detector simultaneously and recorded as a single high-energy photon.
To solve the problem, Mitchell and colleagues used high-sensitivity gamma-ray spectroscopy studies on excited 53Fe isomers generated in a heavy ion accelerator. By transferring the data to the models, they showed that the aggregation contributed little to the 3041-keV line, proving that the transition was of the sixth order. In addition to developing characterization of the energies and powers of the fourth and fifth order transitions, the team also measured the intensity of this transition. According to Mitchell, “these data provide a unique way to test nuclear shell models” because high multipole transitions are fundamentally different from low-order ones.
Source: physics.aps.org/articles/v16/s47
Günceleme: 25/03/2023 14:26