Ⅱ-1. Nuclear Physics
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

Isomeric state studies using the DTAS detector
J. A. Victoria,∗1 V. Vegas,∗1 A. Algora,∗1,∗2 B. Rubio,∗1 J. L. Tain,∗1 A. Tolosa,∗1 J. Agramunt,∗1 E. Nacher,∗1S. E. A. Orrigo,∗1 V. Guadilla,∗3 G. Kiss,∗2 D. Sohler,∗2 I. Kuti,∗2 T. Davinson,∗4 O. B. Hall,∗4 D. M. Kahl,∗4C. G. Bruno,∗4 C. J. Appleton,∗4 P. J. Woods,∗4 S. Nishimura,∗5 N. Fukuda,∗5 H. Suzuki,∗5 D. S. Ahn,∗5H. Baba,∗5 Y. Shimizu,∗5 H. Takeda,∗5 D. Nishimura,∗5 T. Isobe,∗5 M. Kaneko,∗5 S. Kubono,∗5 H. Sakurai,∗5H. Shimizu,∗5 T. Sumikama,∗5 P. Doornenbal,∗5 M. L. Cortes,∗6 Zs. Podolyak,∗7 W. Gelletly,∗7 E. Ganioglu,∗8Y. Fujita,∗9 F. Molina,∗10 J. Liu,∗11 J. Lee,∗11 K. P. Rykaczewski,∗12 M. Wolinska-Cichocka,∗13 M. Labiche,∗14C. J. Griﬃn,∗15 S. Bae,∗16 J. Ha,∗16 and Y. Litvinov∗17In this contribution we present preliminary work
aimed to assess the capabilities of the DTAS detector
to study isomeric states. They are of particular interest, since they can provide information about nuclearstructure. They are also relevant in the analysis of total
absorption data, since they may break the continuityof emitted gamma-ray cascades from high lying states
populated in beta decay. This contribution is related
to experiment NP1612-RIBF147,1) which focuses on thestudy of the beta decay of 100 Sn and neighbouring nuclei using the DTAS modular total absorption spectrometer2) and the AIDA implantation detector.
In the study, we developed analysis tools to look fornuclei with unknown isomeric states in the vicinity of100
Sn using DTAS in combination with the in-ﬂight radioactive ion beam separator BigRIPS. This setup allows
one to study the gamma rays of a particular isomeric decay, looking for time correlations between ions identiﬁed
in BigRIPS and the associated gamma cascade detected
in DTAS, taking advantage of its high eﬃciency. In ouranalysis two dimensional spectra were generated wherein one axis we have the time diﬀerence between the timeof correlated gamma events detected in DTAS modules
and the ion implantation time provided by BigRIPS andon the other axis we have the energy detected by theDTAS individual modules. Isomeric states should beseen in this ﬁgure as gamma transitions (or levels) vanishing as time diﬀerences increase. The very high eﬃciency of the DTAS detector to gamma cascades can be
an asset in this context.
To test the viability of the procedure we have studied
the 98 Cd case, which has a high production rate in ourexperiment and has well known isomeric states. TheFig. 1. Top: 2D ﬁgure corresponding to a 98 Cd gamma cascade detected in DTAS and its energy projection. Bottom: Fit of the the time projection of a gate around the∼1400 keV energy peak marked in the upper panel.

gamma cascade data obtained with the DTAS detector from the de-excitation of 98 Cd isomeric decay populated in the fragmentation reaction can be comparedwith data obtained previously from high resolution experiments using germanium detectors.3)
The comparison between the half-lives from the literature3,4) and the results from our preliminary analysis
shows the validity of the method. In the analysis of thelower states, feeding from above is taking into account.

∗1IFIC, CSIC-Univ. Valencia
Institute for Nuclear Research (ATOMKI)∗3 SUBATECH∗4 School of Physics and Astronomy, University of Edinburgh∗5 RIKEN Nishina Center∗6 INFN-Legnaro∗7 Department of Physics, Surrey University∗8 Department of Physics, University of Istanbul∗9 Osaka University∗10 CCHEN∗11 Department of Physics, University of Hong Kong
∗12 Oak Ridge National Laboratory∗13 Heavy Ion Laboratory, Warsaw University∗14 STFC Daresbury Laboratory∗15 Physical Sciences Division, TRIUMF∗16 Department of Physics and Astronomy, Seoul National University∗17 GSI Helmholtzzentrum für Schwerionenforschung GmbH∗2- 21 -Level
12+8+6+

Literature3,4)224(5) ns
154(16) ns
13(2) ns

Present Work216(7) ns150(3) ns
11(1) ns

In the next step we plan to systematically look forisomers produced in our experiment.
References
1) A. Algora et al., RIKEN Accel. Prog. Rep. 53, 30 (2019).
2) J. L. Tain et al., Nucl. Instrum. Methods Phys. Res. A803, 36 (2015).
3) J. Park et al., Phys. Rev. C 96, 044311 (2017).
4) J. Chen et al., Nucl. Data Sheets 164, 1 (2020).