Discovery of the α-emitting isotope ²¹⁰Pa.

Abstract

Synthesizing isotopes located far away from the line of β-stability is the core research topic in nuclear physics. However, it remains a challenge due to their tiny production cross sections and short half-lives. Here, we report on the observation of a very neutron-deficient isotope ²¹⁰Pa produced via the fusion-evaporation reaction ¹⁷⁵Lu(⁴⁰Ca, 5n)²¹⁰Pa at a newly constructed China Accelerator Facility for Superheavy Elements. The measured α-particle energy of E_α = 8284(15) keV and half-life of <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn> <mo>/</mo> <mn>2</mn></mrow> </msub> <mo>=</mo> <mn>6</mn> <mo>.</mo> <msubsup><mrow><mn>0</mn></mrow> <mrow><mo>-</mo> <mn>1.1</mn></mrow> <mrow><mo>+</mo> <mn>1.5</mn></mrow> </msubsup> </math> ms of ²¹⁰Pa allow us to extend the α-decay systematics and test the predictive power of theoretical models for heavy nuclei near the proton drip line. Based on its unhindered α-decay character, the spin and parity of ²¹⁰Pa is proposed to be (3⁺), supported by the large-scale shell model and cranked shell model calculations. This isotope is discovered with substantial statics within  ∼ 3 days using intensive 2 pμA beam, demonstrating the tremendous capability of the facility for the study of heavy and superheavy nuclei.