Ⅰ. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 53Shell evolution towards 60 Ca: First spectroscopy of 62 Ti†
M. L. Cortés,∗1,∗2 W. Rodriguez,∗1,∗3 P. Doornenbal,∗1 A. Obertelli,∗4,∗5 J. D. Holt,∗6 S. M. Lenzi,∗7J. Menéndez,∗8 F. Nowacki,∗9 K. Ogata,∗10,∗11 A. Poves,∗12 T. R. Rodríguez,∗12 A. Schwenk,∗5,∗13,∗14
J. Simonis,∗15 S. R. Stroberg,∗6,∗16 and K. Yoshida∗17 for the SEASTAR2017 collaboration.
4Energy (MeV)

The study of N = 40 isotones can provide insight
into the mechanisms governing shell evolution. Alongthis isotonic chain diﬀerent behaviors are observed: 68 Ni1)
For Fe and Cr,
shows a high E(2+1 ) and a low B(E2)↓.
+a monotonous decrease of the E(21 ) when approaching N = 40 has been observed,1) while the E(2+1 ) of58, 60
Ti shows a moderate decrease towards N = 40.2,3)
The very exotic 60 Ca, where the Ca isotopic chain meets
the N = 40 isotones, is diﬃcult to reach experimentallyand only recently its existence has been established.4)
Theoretical calculations in the shell-model framework5)
concluded that quadrupole correlations in the N = 40
isotopes give rise to deformed ground states dominatedby intruder neutron orbits beyond the pf shell, leading
to an island of inversion below 68 Ni. On the other hand,symmetry conserving conﬁguration mixing calculations
with the Gogny interaction predict a conservation of theN = 40 gap leading to spherical 62 Ti and 60 Ca.6) In thiswork, the ﬁrst spectroscopy of 62 Ti is presented.
A 345 MeV/nucleon beam of 70 Zn with an average intensity of 240 pnA was fragmented on a Be target to produce 63 V. The isotopes were identiﬁed using BigRIPS7)
and delivered to the 151.3(13) mm long liquid hydrogen target of MINOS8) placed in front of the SAMURAI
magnet. Outgoing 62 Ti fragments were identiﬁed using SAMURAI and associated detectors.9) MINOS wassurrounded by DALI2+ , composed of 226 NaI(Tl) detectors.10,11)
Two peaks were clearly identiﬁed in the Doppler corrected γ-spectrum, and were found to be in coincidence.
Using a 2-dimensional χ2 minimization the energies ofthe transitions were deduced to be 683(10) keV and823(20) keV, which were tentatively assigned to the+++2+1 → 0gs and 41 → 21 transitions, respectively. The+evolution of measured E(2+1 ) and E(41 ) energies for theE(2 +1 ):3E(4 +1 ):LiteratureThis work
LSSM
SCCM
VS-IMSRG

LiteratureThis work
LSSM
SCCM
VS-IMSRG

2E(4 +1 )1E(2 +1 )N=40020222426

283032

Z+Fig. 1. Systematics of E(2+1 ) and E(41 ) for even-even N =40 isotones, including the present measurement. The
black, green, and purple lines represent LSSM, SCCM,and VS-IMSRG calculations, respectively.

N = 40 isotones between Ti and Ge1) is presented in+62Fig. 1. The E(2+Ti have a similar
1 ) and E(41 ) of66
value than the ones measured for Fe, higher than thoseof 64 Cr. This shows the ﬁrst increase of E(2+1 ) along
the N = 40 isotones towards 60 Ca. Large Scale Shell
Model (LSSM) calculations using the LNPS interaction
reproduce very accurately the data, indicating that theisland of inversion in this region extends down to 60 Ca.
Symmetry conserving conﬁguration mixing (SCCM) calculations using the Gogny D1S eﬀective interaction pre64
Cr and 66 Fe which lie very close todict E(2+1 ) for
the LSSM predictions. However, for 62 Ti a larger in+crease of the E(2+1 ) is obtained. For the E(41 ) energies,
the calculations overestimate the experimental values by
about 500 keV, although the minimum value for 64 Cris maintained. Ab initio valence-space in-medium similarity renormalization group (VS-IMSRG) calculations+overestimate the E(2+1 ) and E(41 ) excitation energies in6264
66
Ti, Cr, and Fe, predicting all states as spherical.

Condensed from Phys. Lett. B 800, 135071 (2020)
RIKEN Nishina Center∗2 INFN-Laboratori Nazionali di Legnaro∗3 Universidad Nacional de Colombia∗4 IRFU, CEA, Université Paris-Saclay∗5 Institut für Kernphysik, Technische Universität Darmstadt∗6 TRIUMF∗7 Dipartimento di Fisica e Astronomia, Università di Padova∗8 Center for Nuclear Study, The University of Tokyo∗9 IPHC, CNRS/IN2P3, Université de Strasbourg∗10 RCNP, Osaka University∗11 Department of Physics, Osaka City University∗12 Departamento de Física Teórica, Universidad Autónoma deMadrid∗13 EMMI, GSI Helmholtzzentrum für Schwerionenforschung∗14 Max-Planck-Institut für Kernphysik∗15 Institut für Kernphysik, Johannes Gutenberg-Universität∗16 Department of Physics, University of Washington∗17 Advanced Science Research Center, Japan Atomic Energy
Agency†∗1References

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