Verification of detailed balance for γ absorption and emission in Dy isotopes

Abstract

The photo-neutron cross sections of 162,163 Dy have been measured for the first time in an energy region from the neutron threshold (S n ) up to ≈ 13 MeV. The (γ,n) reaction was induced with quasi-monochromatic laser Compton-scattered γ rays, produced at the NewSUBARU laboratory. The corresponding γ-ray strength functions (γSF) have been calculated from the photo-neutron cross sections. The data are compared to reanalyzed γSFs of 160−164 Dy, which are measured below S n . The excellent agreement with the photo-neutron data at S n confirms the principle of detailed balance. Thus, a complete γSF is established covering in total the energy region of 1 MeV ≤ E γ ≤ 13 MeV. These mid-shell well-deformed dysprosium isotopes all show scissors resonances with very similar structures. We find that our data predict the same integrated scissors strength as (γ, γ ) data when integrated over the same energy range, which shows that the scissors mode very likely is consistent with the generalized Brink hypothesis. Finally, using the γSFs as input in the reaction code TALYS, we have deduced radiative neutron-capture cross sections and compared them to direct measurements. We find a very good agreement within the uncertainties, which gives further support to the experimentally determined γSFs.

Nuclear level densities and γ -ray strength functions in samarium isotopes

“…It is expected that ρ(S n ) will increase as the atomic mass increases however, for 153,155 Sm, a decreasing trend of ρ(S n ) is observed which can be linked to the onset of deformation in these two isotopes. A similar behavior can be seen in deformed Dy isotopes [43]. Table I lists the D 0 and spin-cutoff parameters used for normalizing the experimental level-density data in 147,149 Sm nuclei.…”

Benchmarking the extraction of statistical neutron capture cross sections on short-lived nuclei for applications using the β -Oslo method

“…Also, in recent years, several authors have investigated the applicability of the constant-temperature model for nuclei in various mass regions; see, e.g., Refs. [57][58][59][60][61][62][63]. The best energy range was 0-3.5 MeV based on the quality of the fit to the cumulative level distribution as determined by the respective χ 2 values leading to a temperature, T, of 1.23 (7) MeV and an energy shift, E 0 , of 0.0(2) MeV.…”

Statistical properties of the well deformed Sm153,155 nuclei and the scissors resonance

“…Since then, many heavy deformed even-even and odd-mass rare-earth nuclei have been systematically investigated. So far, the SR mode has been experimentally observed in vibrational and rotational [8], as well as in γ -soft nuclei [9,10] and has also been observed in the actinide region [11][12][13][14][15][16][17], as well as in the rare-earth mass region [4,[18][19][20][21][22][23][24][25][26][27].…”

“…It is suggested that the splitting of the SR may be due to the isovector spin-scissors mode [35], or due to triaxiality [36]. The splitting in the SR has not been reported for any of the rare-earth nuclei studied with the NRF technique [37], with the Oslo method [18][19][20][21]23,24,26,27], or other techniques [4,22,25].…”