1. A new study of the $N=32$ and $N=34$ shell gap for Ti and V by the first high-precision MRTOF mass measurements at BigRIPS-SLOWRI
- Author
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Iimura, S., Rosenbusch, M., Takamine, A., Tsunoda, Y., Wada, M., Chen, S., Hou, D. S., Xian, W., Ishiyama, H., Yan, S., Schury, P., Crawford, H., Doornenbal, P., Hirayama, Y., Ito, Y., Kimura, S., Koiwai, T., Kojima, T. M., Koura, H., Lee, J., Liu, J., Michimasa, S., Miyatake, H., Moon, J. Y., Nishimura, S., Naimi, S., Niwase, T., Odahara, A., Otsuka, T., Paschalis, S., Petri, M., Shimizu, N., Sonoda, T., Suzuki, D., Watanabe, Y. X., Wimmer, K., and Wollnik, H.
- Subjects
Nuclear Experiment - Abstract
The atomic masses of $^{55}$Sc, $^{56,58}$Ti, and $^{56-59}$V have been determined using the high-precision multi-reflection time-of-flight technique. The radioisotopes have been produced at RIKEN's RIBF facility and delivered to the novel designed gas cell and multi-reflection system (ZD MRTOF), which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For $^{56,58}$Ti and $^{56-59}$V the mass uncertainties have been reduced down to the order of $10\,\mathrm{keV}$, shedding new light on the $N=34$ shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species $^{58}$Ti and $^{59}$V. With the new precision achieved, we reveal the non-existence of the $N=34$ empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied $\nu p_{3/2}$ orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the $\nu d_{5/2}$ and $\nu g_{9/2}$ orbits and compare the results with conventional shell model calculations, which exclude the $\nu g_{9/2}$ and the $\nu d_{5/2}$ orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at $N=34$.
- Published
- 2022
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