Mass Measurements of Very Neutron-Deficient Mo and Tc Isotopes and Their Impact on rp Process Nucleosynthesis

Haettner, E., Ackermann, D., Audi, G., Blaum, K., Block, M., Eliseev, S., Fleckenstein, T., Herfurth, F., Hessberger, F. P., Hofmann, S., Ketelaer, J., Ketter, J., Kluge, H. -J., Marx, G., Mazzocco, M., Novikov, Yu. N., Plass, W. R., Rahaman, S., Rauscher, T., Rodriguez, D., Schatz, H., Scheidenberger, C., Schweikhard, L., Sun, B., Thirolf, P. G., Vorobjev, G., Wang, M. and Weber, C. (2011) Mass Measurements of Very Neutron-Deficient Mo and Tc Isotopes and Their Impact on rp Process Nucleosynthesis. Physical Review Letters, 106 (12): 122501. ISSN 0031-9007

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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 neutrondeficient 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.