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

• Published in: arXiv.org 2022-11
• Main Authors: 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, Wollnik, H
• Format: Article
• Language: English
• Subjects: Atomic properties; Energy gap; Mathematical models; Orbits; Radioisotopes; Reflection; Separators; Titanium; Vanadium
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2208.06621

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 \(N=34\).