Production of new neutron-rich isotopes near the $N=60$ isotones ${}_{92}\mathrm{Ge}$ and ${}_{93}\mathrm{As}$ by in-flight fission of a 345 MeV/nucleon ${}_{238}U$ beam

A search for new neutron-rich isotopes near the $N=60$ isotones ${}_{92}\mathrm{Ge}$ and ${}_{93}\mathrm{As}$ has been performed using a 345 MeV/nucleon ${}_{238}U$ beam at the RIKEN Nishina Center RI Beam Factory. Fission fragments produced were analyzed and identified in flight using the large-acceptance two-stage separator BigRIPS. We have observed a total of 15 new neutron-rich isotopes: ${}_{84}\mathrm{Cu}, {}_{86,87}\mathrm{Zn}, {}_{88,89}\mathrm{Ga}, {}_{91,92}\mathrm{Ge}, {}_{93,94,95}\mathrm{As}, {}_{96,97}\mathrm{Se}, {}_{99,100}\mathrm{Br}$, and ${}_{103}\mathrm{Kr}$.