Heavy hydrogen and neutron isotopes

Is the tetraneutron a bound dineutron–dineutron molecule?

“…Adding a pair of neutrons to a nucleus one usually increases the separation energy of the proton. If this rule holds, a simple comparison of the particle-stable tritium and unstable 5 H immediately leads to the conclusion that M( 4 n) > 4M n .…”

“…If the tetraneutron is bound, most probably it will be due to a special four-body attraction in T = 2 states or an exceptional fine tuning of the nucleon-nucleon interaction which does not seem to fit within present nuclear models. It might however be useful to recall an old phenomenological argument [5] against the stability of the tetraneutron. Adding a pair of neutrons to a nucleus one usually increases the separation energy of the proton.…”

“…The possible existence of the tetraneutron has been discussed theoretically by numerous authors already in the 1960s (e.g. [2][3][4][5][6][7][8][9]). The experimental search at that time [10][11][12][13], including the experiments on double pion charge exchange reactions with 4 He [14,15], gave negative results.…”

Neutrons from Deuteron Breakup onHe3

“…24 The first T= 1 state in He 4 has been predicted to lie between 24 and 26 MeV based on results of (p,y) and photonuclear studies. 24,25 None of the spectra in the present study exhibit a peak which could be interpreted as a state in Li 4 . The cross section for formation of a Li 4 state analog to the 20-MeV state seen in the T(d,^)He 4 * reaction 3 should be slightly smaller than that for the He 4 state because of the higher Coulomb barrier, but it would not be expected to be an order of magnitude smaller.…”