Core Insights - The research team from the Institute of Modern Physics of the Chinese Academy of Sciences has made significant progress in the study of rare decay modes of atomic nuclei, successfully observing the new nuclide aluminum-20 and its decay through a rare three-proton emission mode [1][2] Group 1: Research Findings - Over 3,300 nuclides have been discovered, with fewer than 300 being stable nuclides found in nature; the rest are unstable and undergo radioactive decay [1] - Common decay modes include alpha decay, beta decay, beta-plus decay, electron capture, gamma transition, and fission, with many of these modes identified before the mid-20th century [1] - Recent advancements in nuclear physics experiments have led to the discovery of various new decay modes, particularly in neutron-deficient nuclei [1] Group 2: Specific Observations - The aluminum-20 nuclide, located outside the proton drip line and lacking seven neutrons compared to stable aluminum isotopes, is the lightest aluminum isotope observed experimentally to date [2] - The decay of aluminum-20 occurs through a two-step process involving the emission of a proton and then a double proton, with magnesium-19 acting as an intermediate state [2] - The research utilized the Gamow shell model and Gamow coupling method for theoretical calculations, successfully reproducing the decay energy of aluminum-20 and predicting its ground state spin parity [2] Group 3: Theoretical Implications - The study explores isospin symmetry, a fundamental principle in nuclear physics, indicating that mirror nuclei with the same mass number but swapped proton and neutron numbers should exhibit similar energy level structures [2] - The findings suggest a breaking of isospin symmetry in the aluminum-20 and nitrogen-20 mirror nucleus system, which has significant implications for nuclear structure research [2]