N=82 shell quenching of the classical r-process "waiting-point" nucleus 130Cd

Area of Science:

• Nuclear Physics
• Nuclear Astrophysics
• Spectroscopy

Background:

• The rapid neutron-capture process (r-process) is responsible for synthesizing elements heavier than iron.
• Neutron-rich nuclides near the N=82 shell closure, termed 'waiting-point' nuclei, play a critical role in the r-process abundance peaks.
• Understanding the nuclear properties of these waiting-point nuclei is crucial for accurate astrophysical models.

Purpose of the Study:

• To conduct the first beta- and gamma-spectroscopic decay studies of the N=82 r-process waiting-point nuclide 130Cd.
• To investigate the nuclear structure and decay properties of 130Cd and its daughter nucleus 130In.
• To provide experimental data to refine nuclear mass models and astrophysical simulations of the r-process.

Main Methods:

• Utilized CERN/ISOLDE facility for high-resolution beta- and gamma-spectroscopy.
• Employed advanced techniques for achieving the highest possible isotopic selectivity for 130Cd.
• Analyzed decay chains to determine energy levels, transition probabilities, and Q(beta) values.

Main Results:

• Observed an unexpectedly high excitation energy (2.12 MeV) for the [pi g(9/2) x nu g(7/2)] 1(+) level in 130In, populated by the dominant Gamow-Teller transition.
• Measured a significantly high Q(beta) value of 8.34 MeV for 130Cd decay.
• The experimental Q(beta) value aligns with theoretical predictions that incorporate N=82 shell quenching.

Conclusions:

• The experimental findings challenge existing nuclear models and highlight the need for improved theoretical descriptions of nuclei near the N=82 shell closure.
• The high Q(beta) value and specific level structure in 130In have significant implications for the production yields of r-process elements around A ≈ 130.
• These results contribute to a more accurate understanding of the nucleosynthesis pathways responsible for the cosmic abundance of heavy elements.