On a possible observation of "dihelion" in dissociation of relativistic   $^9$C nuclei
  Nuclear track emulsion is exposed to 1.2 A $^9$C GeV nuclei. Pairs of 2$^3$He nuclei having unusually narrow opening angles are observed in channel $^9$C $\rightarrow$ 3$^3$He pointing to the possible 2$^3$He resonance near the production threshold. 
D. A. Artemenkov, N. K. Kornegrutsa, D. O. Krivenkov, R. Stanoeva and   P. I. Zarubin
nucl-ex