Decay spectroscopy in heavy and superheavy nuclei: the SHEXI project and isomeric states in Ra nuclei

by Margarida Paulino (1^st year PhD student)

The region of heavy and superheavy nuclei (SHN) will be one of the study areas of the S3 separator at GANIL. They are formed often with low cross-sections, which enhances the importance of using separators with high transmission and high mass resolutions for possibly needed particle identification, and detection setups with high efficiencies.

Two experimental setups dedicated to studying the structure of heavy and superheavy nucleiwill be presented: SIRIUS and its future upgrade SHEXI [1], in GANIL, and RITU, in JYFL [2].

The SHEXI project consists of an upgrade of SIRIUS to improve the detection efficiency of low energy X-rays [3]. In SHN, X-rays are mostly emitted as a consequence of electromagnetic decay. When the energy difference between two excited nuclear states is smaller than the binding energy of the K electrons, the emission of L-line X-rays becomes dominant, and detecting them can be an important tool for both isotope identification and studying the nuclear structure of these nuclei.

During an experiment done at RITU dedicated to decay spectroscopy of ²¹⁷Pa, the reaction ⁴⁰Ar+^natYb, used for calibration purposes, yielded information on several meta-stable states of neutron-deficient Ra nuclei. The results were obtained using the focal plane detector of RITU, GREAT [4]. Isomers can provide important insights into the excitation energy, spin, and parity of single-particle levels, and preliminary results obtained on these states will be presented.

References:
[1] F. Dechery et al., NIM-B 376 (2016)
[2] M. Leino et al., NIM-B 99 653-656 (1995)
[3] K. Hauschild, APPB Proc. Suppl. 18 2-A28 (2025)
[4] J. Sarén, J. Uusitalo and H. Joukainen, NIM-B 541 33-36 (2023)