First observation of the d + d. -->. /sup 4/He + eta/sup 0/ reaction

The first observation of the reaction dd..--> cap alpha..eta is reported. The missing mass spectrum in dd..--> cap alpha..X shows an enhancement at the ..cap alpha.. momentum corresponding to the eta mass. The corresponding c.m. cross section is 0.25 +- 0.10 nb/sr for eta's produced at 146/sup 0/ in the c.m.