Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis

TL;DR

This study measures the masses of neutron-deficient Mo and Tc isotopes, revealing shifts that impact astrophysical rp process nucleosynthesis, including the potential formation of a ZrNb cycle that limits element synthesis beyond Nb.

Contribution

It provides new mass measurements of proton-rich Mo and Tc isotopes, showing a systematic shift affecting nucleosynthesis models and suggesting the possibility of a ZrNb cycle in the rp process.

Findings

Masses of ten proton-rich nuclides measured with Penning trap.

Observed mass surface shift up to 1.6 MeV compared to 2003 evaluation.

Low alpha-separation energies suggest formation of a ZrNb cycle.

Abstract

The masses of ten proton-rich nuclides, including the N=Z+1 nuclides 85-Mo and 87-Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical X-ray bursts. Surprisingly low alpha-separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.