  We investigate the long-range interactions between two neutrons utilizing
recent data on the neutron static and dynamic electric and magnetic dipole
polarizabilities. The resulting long-range potentials are used to make
quantitative comparisons between the collisions of a neutron with a neutron and
a neutron with a proton. We also assess the importance of the first pion
production threshold and first excited state of the nucleon, the
$\Delta$-resonance ($J^{\pi}$ = + 3/2, I = 3/2). We found both dynamical
effects to be quite relevant for distances r between ~ 50 fm up to ~$10^3$ fm
in the nn system, the neutron-wall system and in the wall-neutron-wall system,
reaching the expected asymptotic limit beyond that. Relevance of our findings
to the confinement of ultra cold neutrons inside bottles is discussed.

Nuclear Theory;Atomic Physics