New search for {sup 26}O

An attempt was made to find the very neutron-rich isotope {sup 26}O among the fragmentation products of a 90 MeV/nucleon {sup 40}Ar beam. This isotope has been predicted to be bound but was not observed in a previous experiment by Guillemaud-Mueller {ital et} {ital al}. As part of the search, the momentum distributions of all the oxygen isotopes in the range from {sup 17}O to {sup 24}O were carefully determined so that the optimum separator setting for {sup 26}O could be used. From an extrapolation of the counting rates of the lighter oxygen isotopes, we expected to observe several hundred events of {sup 26}O during the measurement. However, no events could be attributed to {sup 26}O, thus indicating the particle instability of this isotope. The results for the production cross sections of 72 neutron-rich isotopes, ranging from {sup 38}P to {sup 11}B, are presented and compared to predictions. {copyright} {ital 1996 The American Physical Society.}