Neutron packed together

[Forestman]

I meant to title it "Neutrons packed together"

Since neutrons can be packed together in a neutron star, would it be possible to take say five neutrons and pack them together and make a neutroium nucleus. And if not, how come?

[Vanadium 50]

Gravity in a neutron star is strong enough to overcome the repulsion between neutrons. The strong force is not.

[malawi_glenn]

The strong force is not enough to form bound state of neutrons, the only bound nucleon-nucleon state is deuterium. So you need A LOT of neutrons to form a bound state, a state which is bound by gravity, as Vanadium suggested

[Bob_for_short]

A purely neutronic nucleus is not stable - is decays even faster than a free neutron itself.

But you can take several very slow neutrons and put them in a trap with the reflecting walls (a box). Such neutrons are "large" - their De Broglie wave length is big. If the trap size is small enough, you can obtain "overlapping" neutrons in a box. They do not form a bound state but rather manifest their fermionic nature (filling the "box" states is specific here).

Bob.

[Bob S]

The strong force is not enough to form bound state of neutrons, the only bound nucleon-nucleon state is deuterium. So you need A LOT of neutrons to form a bound state, a state which is bound by gravity, as Vanadium suggested
There were experiments done in the late 1960s (by Abashian, Booth, and Crowe, or ABC) looking for di neutron states in scattering protons off of deuterium at low energies. Search web "abashian booth crowe ABC experiment"

[Lantzelot]

Neutron clusters have been under consideration in some experimental work, see for instance
PHYSICAL REVIEW C, VOLUME 65, 044006, F. M. Marques et al.
where tetra-neutron states are considered in the breakup from 14Be.
If they exist they will be very short-lived, one would rather see traces of it when it dissolves instead of a bound neutron cluster. But it is of interest in order to better understand clustering effects within atomic nuclei.