2014/09/11 by B. A. Brown, B. Alex Brown, A. C. Larsen · 2 citations
Physics and Astronomy · #Astronomical and nuclear sciences #Atomic and Molecular Physics #Atomic physics #Energy (signal processing) #Excitation #Nuclear physics research studies #Physics #Quantum mechanics #Spectral line #nucl-th
paper · pdf · doi:10.1103/physrevlett.113.252502
published as Phys. Rev. Lett. 113, 252502 (2014) · 5 pages, 5 figures
arxiv created 2014/09/11 · openalex publication_date 2014/12/19 · arxiv updated 2014/12/24 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
A strong enhancement at low \ensuremathγ-ray energies has recently been discovered in the \ensuremathγ-ray strength function of 56,57Fe. In this work, we have for the first time obtained theoretical \ensuremathγ decay spectra for states up to \ensuremath≈8 MeV in excitation for 56,57Fe. We find large B(M1) values for low \ensuremathγ-ray energies that provide an explanation for the experimental observations. The role of mixed E2 transitions for the low-energy enhancement is addressed theoretically for the first time, and it is found that they contribute a rather small fraction. Our calculations clearly show that the high-\ensuremathℓ(=f) diagonal terms are most important for the strong low-energy M1 transitions. As such types of 0\ensuremathℏ\ensuremathω transitions are expected for all nuclei, our results indicate that a low-energy M1 enhancement should be present throughout the nuclear chart. This could have far-reaching consequences for our understanding of the M1 strength function at high excitation energies, with profound implications for astrophysical reaction rates.