Further Evidence for the Nonexistence of Particle-Stable Tetraneutrons

A search was made for the occurrence of particle-stable tetraneutrons in the fast-deuteron-induced fission of uranium. This process is known to give a high yield of alphas and tritons. In order to deduce the presence of tetraneutrons, the following hypothetical reactions were investigated: ${\mathrm{N}}^{14}(n^4, n){\mathrm{N}}^{17}$, ${\mathrm{O}}^{16}(n^4, t){\mathrm{N}}^{17}$, ${\mathrm{Mg}}^{26}(n^4, 2n){\mathrm{Mg}}^{28}$, ${\mathrm{Rh}}^{103}(n^4, 2n){\mathrm{Rh}}^{105}$, ${\mathrm{Bi}}^{209}(n^4, n){\mathrm{Bi}}^{212}$ and ${\mathrm{Bi}}^{209}(n^4, 2n){\mathrm{Bi}}^{211}$. No evidence for tetraneutrons was found. The upper limits of tetraneutron yields per alpha obtained from the above reactions are: 2×${10}^{-8\mathrm{}}$, 3×${10}^{-4\mathrm{}}$, 3×${10}^{-5\mathrm{}}$, 3×${10}^{-4\mathrm{}}$, 1×${10}^{-6\mathrm{}}$, and 1×${10}^{-8\mathrm{}}$, respectively. It seems reasonable to conclude from these results that the existence of tetraneutrons is most unlikely.