Evolution of the γ -ray strength function in neodymium isotopes

Abstract

The experimental γ -ray strength functions (γ SFs) of 142,[144][145][146][147][148][149][150][151] Nd have been studied for γ -ray energies up to the neutron separation energy using the Oslo method. The results represent a unique set of γ SFs for an isotopic chain with increasing nuclear deformation. The data reveal how the low-energy enhancement, the scissors mode, and the pygmy dipole resonance evolve with nuclear deformation and mass number. This indicates that the mechanisms behind the low-energy enhancement and the scissors mode are decoupled from each other.

Magnetic dipole γ-ray strength functions of heavy nuclei in the configuration-interaction shell model

“…The LEE was observed experimentally in lanthanide isotopes [6][7][8] in experiments based on the Oslo method, but these experiments cannot separate the E1 and M1 components of the γSF. A detailed comparison with such experiments requires the calculation of the E1 γSF.…”

“…γ-ray strength functions (γSF) [1], along with level densities, are necessary input to the Hauser-Feshbach theory [2] of compound nucleus reactions. In recent years, a low-energy enhancement (LEE) was observed in the γSFs of mid-mass nuclei [3][4][5] and in several rareearth nuclei [6][7][8]. If the LEE persists in heavy neutron-rich nuclei, it would have significant effects on the calculations of r-process nucleosynthesis by enhancing radiative neutron capture rates near the neutron drip line [9].…”

Photon strength functions and nuclear level densities: invaluable input for nucleosynthesis

“…Initially observed in A < 100 nuclei, e.g. [18,25], it has recently been observed in some heavier nuclei as well [14,26,38]. Since its discovery, this so-called 'upbend' has been independently confirmed [39] and shown to have dipole multipolarity [14] and magnetic polarization although not conclusively [40].…”

“…The M ⁢ 1 scissors mode strength is generally found to be concentrated at E γ ∼ 3 MeV as measured in several deformed nuclei with Oslo- [26,27] and NRF-type [28] experiments. For the heaviest nuclei, some PSFs have revealed a splitting of the scissors mode from the Oslo method [17,29,30] and NRF experiments [31,32].…”

“…( γ , γ ′), probes which reveal a separation into isoscalar and isovector excitations. The PDR is also populated in lower-energy charged-particle reactions as demonstrated for 74 Ge [24] or through Oslo method measurements [25,26] although the latter does not generally allow for an unambiguous identification as a E ⁢ 1 PDR.…”