We performed the first direct mass measurements of neutron-rich scandium, titanium, and vanadium isotopes around the neutron number 40 at the RIKEN RI Beam Factory using the time-of-flight magnetic-rigidity technique. The atomic mass excesses of ${}^{58-60}\mathrm{Sc}$, ${}^{60-62}\mathrm{Ti}$, and ${}^{62-64}\mathrm{V}$ were measured for the first time. The experimental results show that the two-neutron separation energies in the vicinity of ${}^{62}\mathrm{Ti}$ increase compared to neighboring nuclei. This shows that the masses of Ti isotopes near $N=40$ are affected by the Jahn-Teller effect. Therefore, a development of Jahn-Teller stabilization appears below the Cr isotopes, and the systematics in Sc, Ti, and V isotopes suggest that ${}^{62}\mathrm{Ti}$ is located close to the peak of the Jahn-Teller effect.

• Received 3 April 2020
• Revised 12 June 2020
• Accepted 21 July 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.122501