Identification of new transitions and mass assignments of levels in $^{143--153}\mathrm{Pr}$

Identification of new transitions and mass assignments of levels in ${}^{143 - 153}\Pr$

E. H. Wang et al.

Phys. Rev. C 92, 034317 – Published 16 September 2015; Erratum Phys. Rev. C 109, 029902 (2024)

Abstract

Background: The previously reported levels assigned to ${}^{151, 152, 153}\Pr$ have recently been called into question regarding their mass assignment.

Purpose: We clarify the above questioned level assignments by measuring $γ$ transitions tagged with $A$ and $Z$ in an in-beam experiment in addition to the measurements from ${}^{252}{Cf}$ spontaneous fission (SF) and establish new spectroscopic information from $N = 84$ to $N = 94$ in the Pr isotopic chain.

Methods: The isotopic chain ${}^{143 - 153}\Pr$ has been studied from the spontaneous fission of ${}^{252}{Cf}$ by using Gammasphere and also from the measurement of the prompt $γ$ rays in coincidence with isotopically identified fission fragments using VAMOS++ and EXOGAM at Grand Accelerateur National d'Ions Lourds (GANIL). The latter were produced using ${}^{238}U$ beams on a ${}^{9}{Be}$ target at energies around the Coulomb barrier. The $γ − γ − γ − γ$ data from ${}^{252}{Cf}$ (SF) and those from the GANIL in-beam $A$ - and $Z$ -gated spectra were combined to unambiguously assign the various transitions and levels in ${}^{151, 152, 153}\Pr$ and other isotopes.

Results: A band of 3 new transitions added to the known level in ${}^{145}\Pr$ , 9 new transitions in two new bands in ${}^{147}\Pr$ , 6 new transitions in a new level scheme for ${}^{148}\Pr$ , two new bands with 17 new transitions in ${}^{149}\Pr$ , and two new bands with 11 new transitions in ${}^{150}\Pr$ were identified by using $γ − γ − γ$ and $γ − γ − γ − γ$ coincidences and $A$ and $Z$ -gated $γ − γ$ spectra. The transitions and levels previously assigned to ${}^{151, 153}\Pr$ have been confirmed by the $(A, Z)$ -gated spectra. Small changes have been made to their original level schemes. The transitions previously assigned to ${}^{152}\Pr$ are now assigned to ${}^{151}\Pr$ on the basis of the $(A, Z)$ -gated spectra. Two new bands with 20 new transitions in ${}^{152}\Pr$ and one new band with 7 new transitions in ${}^{153}\Pr$ are identified from the $γ − γ − γ − γ$ coincidence spectra and the $(A, Z)$ -gated spectrum. In addition, new $γ$ rays are also reported in ${}^{143 - 146}\Pr$ .

Conclusions: New levels of ${}^{145, 147 - 153}\Pr$ have been established, reliable mass assignments of the levels in ${}^{151, 152, 153}\Pr$ have been given in the present work, and new transitions have been identified in ${}^{143 - 146}\Pr$ showing the new avenues that are opened by combining the two experimental approaches.