A search for new proton-rich isotopes using projectile fragmentation of a 345-MeV/nucleon ${}^{124}\mathrm{Xe}$ beam has been performed with the BigRIPS in-flight separator at the RIKEN Nishina Center RI Beam Factory. Projectile fragments were identified by measuring the time of flight, magnetic rigidity, and energy loss in the BigRIPS separator. Projectile fragments then were transported downstream of the BigRIPS separator and re-identified by measuring the time of flight and total kinetic energy. Through such particle re-identification, we have discovered four new isotopes ${}^{81,82}\mathrm{Mo}$ and ${}^{85,86}\mathrm{Ru}$ located near the proton drip line. The ${}^{76}\mathrm{Y}$ and ${}^{78}\mathrm{Zr}$ isotopes near the proton drip line also were identified, supporting the previous report on their discovery. Furthermore, we have obtained the first clear evidence for the particle instability of ${}^{103}\mathrm{Sb}$. Based on the systematics of measured production yields, the upper limit values were evaluated for the half-lives of the particle-unbound isotopes ${}^{81}\mathrm{Nb},{}^{85}\mathrm{Tc}$, and ${}^{103}\mathrm{Sb}$.

• Received 19 October 2016
• Revised 24 June 2017

DOI:https://doi.org/10.1103/PhysRevC.96.034604