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Abstract

Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of ⁸²Zr and ⁸⁴Nb were measured for the first time with an uncertainty of ∼10 keV, and the masses of ⁷⁹Y, ⁸¹Zr, and ⁸³Nb were re-determined with a higher precision. The latter are significantly less bound than their literature values. Our new and accurate masses remove the irregularities of the mass surface in this region of the nuclear chart. Our results do not support the predicted island of pronounced low α separation energies for neutron-deficient Mo and Tc isotopes, making the formation of Zr–Nb cycle in the rp-process unlikely. The new proton separation energy of ⁸³Nb was determined to be 490(400) keV smaller than that in the Atomic Mass Evaluation 2012. This partly removes the overproduction of the p-nucleus ⁸⁴Sr relative to the neutron-deficient molybdenum isotopes in the previous νp-process simulations.