>I wonder why pure small neutral nuclei (e.g. only 4 neutrons instead
>of 2 protons and 2 neutrons like in He) seemed not to exist. I know
>that giant stars can transform in so called "neutron stars", that
>consist only of neutrons.
>These kind of single neutral nuclei normally should be more likely and
>even more stable, because there is no electromagnetical repulsive
>forces between each other like in normal nuclei. It is clear that
>single neutrons are not stable and decay within about 10 Min., but
>bounded neutrons should exist. In standardmodel of particle physics
>all quarks are equal to the strength of the strong interaction. The
>strong force do not distinguish between the flavor, so there is no
>sensible reason why neutral nuclei should not exist.
>Maybe someone knows the answer...
They decay for the same reason that the single neutron does.
With strong interaction it wouldn't, but with weak interaction, it does.