Scientists Discover Mysterious Nuclear “Bump” Challenging Existing Physics Models

Scientists at the University of Jyväskylä’s Accelerator Laboratory have precisely measured the atomic masses of radioactive lanthanum isotopes, uncovering an unexpected anomaly in their nuclear binding energies. This discovery sheds light on the formation of elements heavier than iron and raises questions about nuclear structure.

At the IGISOL facility, researchers produced short-lived, neutron-rich lanthanum isotopes, making their precise mass measurements a major breakthrough.

“Using phase-imaging ion cyclotron resonance, we measured six lanthanum isotopes with exceptional precision, including the first-ever measurements of lanthanum-152 and lanthanum-153,” says Professor Anu Kankainen, who led the study.

A Phenomenon Observed in Neutron Star Collisions

Analyzing precise mass data, researchers examined lanthanum isotopes’ neutron separation energies, which reveal nuclear structure insights.

“This factor is key for calculating neutron-capture rates in the rapid r process during neutron-star mergers, as seen in the GW170817 kilonova,” Kankainen explains.

They discovered a sharp “bump” when neutron count rose from 92 to 93—an unexplained anomaly.

“I was astonished,” says PhD researcher Arthur Jaries. “Current models can’t explain it. It may stem from a sudden nuclear structure shift, requiring further study with laser or nuclear spectroscopy.”

A Need for Improved Theoretical Models

These precise mass measurements significantly impacted astrophysical models, altering neutron-capture reaction rates by up to 35% and reducing mass-related uncertainties by a factor of 80 in extreme cases.

“These refined reaction rates are crucial for understanding the formation of the rare-earth abundance peak in the r process,” Kankainen notes. “More importantly, they reveal that current nuclear mass models fail to predict this anomaly, highlighting the need for further theoretical advancements.”

Read Original Article: Scitechdaily

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