system
Given the following post, respond as if you're commenting on Reddit:
human
Why are there no nuclei consisting exclusively of neutrons?
gpt
There are no bound nuclei, but there are resonances like the dineutron. There is also the more controversial tetraneutron.

But these systems are unbound, and decay with half-lives on the order of 10^(-21) seconds.

If you take a system of two neutrons at low relative momentum, there is an attractive interaction between them due to the residual strong force. However the attraction is not strong enough to form bound states.