An experimental observation of the 4n-decay of 28O was recently published in Nature:
https://www.nature.com/articles/s41586-023-06352-6
This finding is a convincing evidence of the instability of the Z = 8, N = 20 doubly magic nucleus 28O, a significant challenge of the traditional shell model.
Three researchers at CENS are co-authors of this achievement: J. W. Hwang, S. Kim and L. Stuhl.
J. W. Hwang commented in one of the news interviews that the primary obstacle was the simultaneous detecton of 4 neutrons from 28O.
Corresponding news links:
https://www.nature.com/articles/d41586-023-02485-w (Nature - News and Views)
http://m.dongascience.com/news.php?idx=61435 (동아사이언스, in Korean)
https://www.donga.com/news/article/all/20230903/120999014/1 (동아일보, in Korean)
Center for Exotic Nuclear Studies