In an experiment at the SISSI/LISE facility of GANIL, we used the projectile fragmentation of a ${}^{78}\mathrm{Kr}$ primary beam at 73 MeV/nucleon to produce new isotopes of astrophysical interest. We obtained clear evidence for the existence of the five new isotopes ${}^{60}\mathrm{Ga}$, ${}^{64}\mathrm{As}$, ${}^{69,70}\mathrm{Kr}$, and ${}^{74}\mathrm{Sr}$. However, we did not find any evidence for ${}^{69}\mathrm{Br}$, whereas comparable nuclei were observed with more than 1000 counts. The isotope ${}^{69}\mathrm{Br}$ is thus deduced to be a proton-unbound nucleus with a half-life shorter than about 100 ns. The influence of these results on our understanding of the astrophysical RP process is discussed.

• Received 12 January 1995

DOI:https://doi.org/10.1103/PhysRevLett.74.4611