Researchers from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences and their collaborators have synthesized a new isotope—protactinium-210—for the first time. It is the most neutron-deficient isotope of protactinium synthesized to date. Their findings were published in Nature Communications on May 29.

The atomic nucleus is a quantum many-body system composed of protons and neutrons. Synthesizing and studying new nuclides is a frontier research topic in nuclear physics. Through this research, scientists can explore the limits of the existence of nuclei and deepen our understanding of the fundamental properties of matter.

Theoretical predictions suggest the existence of around 7,000 nuclides, yet only about 3,300 have been experimentally synthesized and observed so far.

"In the extremely neutron-deficient actinide region, the production cross-section of new isotopes is extremely low. Moreover, their half-lives are very short—down to milliseconds or even microseconds—which poses great challenges for experimental studies," said ZHANG Mingming, an associate professor at IMP and first author of the study.

The experiment was conducted at the China Accelerator Facility for Superheavy Elements (CAFE2). The calcium-40 beam was accelerated to bombard a lutetium-175 target. Through a fusion-evaporation reaction, the researchers successfully synthesized and identified the new isotope protactinium-210 using the gas-filled recoil separator, Spectrometer for Heavy Atoms and Nuclear Structure-2 (SHANS2).

They successfully measured the α-decay properties of protactinium-210 and extended the α-decay systematics in this region. The results are in good agreement with theoretical calculations for heavy nuclei at and beyond the proton drip line.

"Despite the low production cross-section of protactinium-210 (only about 7 picobarns), we successfully observed 23 events. This validates the facility's capability for the study of heavy and superheavy nuclei, laying the foundation for experiments on synthesizing new elements," said Prof. MA Long of IMP.

This work was conducted in collaboration with researchers from the University of Chinese Academy of Sciences, Advanced Energy Science and Technology Guangdong Laboratory, Shandong University, and other institutions.

DOI: https://doi.org/10.1038/s41467-025-60047-2

Fig：a α particles following the implanted residues within a time window of 30 ms. Note that the isotopes of ²¹³Rn and ²¹⁴Fr were transfer products due to the small contamination of ²⁰⁹Bi material in our targets. b Two-dimensional scatter plot of parent and child α-particle energies for correlated ER-α1 − α2 events detected in the DSSD. The searching time windows were 30 ms for the ER-α1 pair and 150 ms for the α1-α2 pair. The decay events from ²¹⁰Pa are indicated with red arrow.