Fast-timing Measurement in 96Pd : Improved Accuracy for the Lifetime of the 4+1 State

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY 4.0 https://creativecommons.org/licenses/by/4.0/ Fast-timing Measurement in 96Pd : Improved Accuracy for the Lifetime of the 4+1 State © Authors 2023 Published version Yaneva, A.; Jazrawi, S.; Das, B.; Mikolajczuk, M.; Górska, M.; Regan, P. H.; Cederwall, B.; Jolie, J.; Benzoni, G.; Albers, H. M.; Alhomaidhi, S.; Arici, T.; Banerjee, A.; Chishti, M. M. R.; Davinson, T.; Gerl, J.; Hall, O.; Hubbard, N.; Kojouharov, I.; Mistry, A. K.; Polettini, M.; Rudigier, M.; Sahin, E.; Schaffner, H.; Sharma, A.; Wollersheim, H. J.; Boutachkov, P.; Dickel, T.; Haettner, E.; Heggen, H.; Hornung Ch.; Knöbel, R.; Kostyleva, D.; Kurz, N.; Kuzminchuk, N.; Mukha, I.; Pietri, S.; Plass, W. R.; Podolyak, Zs.; Scheidenberger, C.; Tanaka, Y. K.; Vesic, J.; Weick, H.; Ahmed, U.; Aktas, Ö.; Algora, A.; Appleton, C.; Benito, J.; Blazhev, A.; Bracco, A.; Bruce, A.; Brunet, M.; Canavan, R.; Esmaylzadeh, A.; Fraile, L. M.; Häfner, G.; Hucka, K. P.; John, P. R.; Kahl, D.; Karayonchev, V.; Kern, R.; Kosir, G.; Lozeva, R.; Napiralla, P.; Nara Singh, B. S.; Page, R. D.; Petrache, C. M.; Pietralla, N.; Regis, J.-M.; Rösch, H.; Ruotsalainen, P.; Sanchez-Temble, V.; Sexton, L.; Shearman, R.; Si, M.; Werner, V.; Wiederhold, J.; Wimmer, K.; Witt, W.; Woods, P.; Zimba, G. Yaneva, A., Jazrawi, S., Das, B., Mikolajczuk, M., Górska, M., Regan, P. H., Cederwall, B., Jolie, J., Benzoni, G., Albers, H. M., Alhomaidhi, S., Arici, T., Banerjee, A., Chishti, M. M. R., Davinson, T., Gerl, J., Hall, O., Hubbard, N., Kojouharov, I., . . . Zimba, G. (2023). Fast-timing Measurement in 96Pd : Improved Accuracy for the Lifetime of the 4+1 State. In M. Matejska-Minda, P. Bednarczyk, & M. Kmiecik (Eds.), Zakopane Conference on Nuclear Physics : Extremes of the Nuclear Landscape : Zakopane, Poland, August 28–September 4, 2022 (16, Article A30). Jagiellonian University. Acta Physica Polonica B : Proceedings Supplement. https://doi.org/10.5506/APhysPolBSupp.16.4-A30 2023 Acta Physica Polonica B Proceedings Supplement 16, 4-A30 (2023) FAST-TIMING MEASUREMENT IN 96Pd: IMPROVED ACCURACY FOR THE LIFETIME OF THE 4+ 1STATE∗ A. Yanevaa,b, S. Jazrawic,d, B. Dasb,e, M. Mikolajczukb,f M. Górskab, P.H. Reganc,d, B. Cederwalle, J. Joliea G. Benzonig, H.M. Albersb, S. Alhomaidhib,h,i,j, T. Aricib A. Banerjeeb, M.M.R. Chishtic, T. Davinsonk, J. Gerlb O. Hallk, N. Hubbardb,h,i, I. Kojouharovb, A.K. Mistryb,h,i M. Polettinig,l, M. Rudigieri, E. Sahinb,h,i, H. Schaffnerb A. Sharmam, H.J. Wollersheimb, P. Boutachkovb, T. Dickelb E. Haettnerb, H. Heggenb, Ch. Hornungb, R. Knöbelb D. Kostylevab, N. Kurzb, N. Kuzminchukb, I. Mukhab S. Pietrib, W.R. Plassb, Zs. Podolyakc, C. Scheidenbergerb Y.K. Tanakan, J. Vesico, H. Weickb, U. Ahmedi, Ö. Aktase A. Algorap,q, C. Appletonk, J. Benitor, A. Blazheva A. Braccog,l, A. Bruces, M. Brunetc, R. Canavanc,d A. Esmaylzadeha, L.M. Frailer, G. Häfnera,t, K.P. Huckai P.R. Johni, D. Kahlk, V. Karayoncheva, R. Kerni, G. Kosiro,u R. Lozevat, P. Napirallai, B.S. Nara Singhv, R.D. Pagew C.M. Petrachet, N. Pietrallai, J.-M. Regisa, H. Röschi P. Ruotsalainenx, V. Sanchez-Tembler, L. Sextonk R. Shearmand, M. Sit, V. Wernerh,i, J. Wiederholdi K. Wimmerb, W. Witti, P. Woodsk, G. Zimbax on behalf of DESPEC Collaboration aInstitut für Kernphysik der Universität zu Köln, 50937 Köln, Germany bGSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany cDepartment of Physics, University of Surrey, Guildford, GU2 7XH, UK dNational Physical Laboratory, Teddington, Middlesex, TW11 0LW, UK eKTH Royal Institute of Technology, Stockholm, Sweden fFaculty of Physics, University of Warsaw, 00-681 Warsaw, Poland gINFN, Sezione di Milano, Milano, Italy hTechnische Universität Darmstadt, Department of Physics Institute for Nuclear Physics, Schlossgartenstr. 9, 64289 Darmstadt, Germany iHelmholtz Forschungsakademie Hessen für FAIR (HFHF) GSI Helmholtzzentrum für Schwerionenforschung Campus Darmstadt, 64289 Darmstadt, Arheilgen jKing Abdulaziz City for Science and Technology (KACST) P.O. Box 6086, Riyadh 11442, Saudi Arabia kSchool of Physics and Astronomy, University of Edinburgh Edinburgh EH9 3FD, UK lDipartimento di Fisica, Universita degli Studi di Milano, Milano, Italy (4-A30.1) Acta Physica Polonica B Proceedings Supplement 16, 4-A30 (2023) mDepartment of Physics, Indian Institute of Technology Ropar Rupnagar 140001, Punjab, India nHigh-Energy Nuclear Physics Laboratory, RIKEN, 351-0198 Saitama, Japan oJožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia pInstituto de Fisica Corpuscular, CSIC-Universidad de Valencia 46071 Valencia, Spain qInstitute for Nuclear Research (ATOMKI) Bem ter 18/c, 4026 Debrecen, Hungary rGrupo de Física Nuclear and IPARCOS, Universidad Complutense de Madrid CEI Moncloa, 28040 Madrid, Spain sSchool of Computing Engineering and Mathematics, University of Brighton BN2 4AT Brighton, UK tUniversité Paris-Saclay, IJCLab, CNRS/IN2P3, 91405 Orsay, France uFaculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia vSchool of Computing, Engineering and Physical Sciences University of the West of Scotland, PA1 2BE Paisley, UK wDepartment of Physics, Oliver Lodge Laboratory, University of Liverpool Liverpool L69 7ZE, UK xUniversity of Jyväskylä, Seminaarinkatu 15, 40014 Jyväskylän yliopisto, Finland Received 30 November 2022, accepted 10 January 2023, published online 22 March 2023 Direct lifetime measurements via γ–γcoincidences using the FATIMA fast-timing LaBr3(Ce) array were performed for the excited states below previously reported isomers. In the N= 50 semi-magic 96Pd nucleus, lifetimes below the Iπ= 8+seniority isomer were addressed as a benchmark for further analysis. The results for the Iπ= 2+and 4+states confirm the published values. Increased accuracy for the lifetime value was achieved for the 4+state. DOI:10.5506/APhysPolBSupp.16.4-A30 1. Introduction In March 2020, the first experiment of the DEcay SPECtroscopy (DESPEC) setup [1] as part of the FAIR Phase-0 campaign was performed at the GSI Helmholtzzentrum für Schwerionenforschung. The focus of this experiment was the measurement of electromagnetic transition rates between excited states below known isomers using the fast-timing technique [2–5]. In particular, the main goal was an investigation of the decay of the 14+, T1/2= 499(13) ns isomer in 94Pd [5–8]. In the same experiment, lifetimes in several N= 50 isotones were studied for the first time [9,10]. In addition, the known isomeric decay of the Iπ= 8+state in 96Pd was observed and used as a reference case for other lifetime measurements in order to verify the ∗Presented at the Zakopane Conference on Nuclear Physics, Extremes of the Nuclear Landscape, Zakopane, Poland, 28 August–4 September, 2022. (4-A30.2) Fast-timing Measurement in 96 Pd: Improved Accuracy . . . 4-A30.3 setup and the analysis method. Indeed, 96Pd, with its four proton holes in the doubly-magic 100Sn core, has proven to be attractive for nuclear structure studies in the last four decades [3,11–13]. However, the lifetimes of the intermediate states below the isomer were reported only recently [12] and the conservation of the seniority quantum number was addressed. The last work indicated a seniority breakdown based in particular on the lifetime measurement of the 4+state, which, therefore, called for independent experimental verification. 2. Experimental details The isomeric states in the nuclei of interest were produced by the fragmentation of a 124Xe primary beam at 982 AMeV impinging on a 4 g/cm2 thick 9Be target [7]. The cocktail beam of secondary particles was analyzed in the FRagment Separator (FRS) [14]. Standard tracking detectors and separation methods were used to select and identify the species of interest on an event-by-event basis in terms of their mass-to-charge ratio (A/Q) and atomic number (Z). Ions arriving at the final focal plane of the FRS were implanted in the Advanced Implantation Detector Array (AIDA) active stopper [15]. AIDA is situated in the center of the DESPEC setup in between two β-plastic scintillation detectors for fast β-decay time reference [1]. For registering γ-rays, 36 LaBr3(Ce) detectors (FATIMA) [16] and 6 triple cluster HPGe detectors (GALILEO) [17,18] were used surrounding the implantation setup. The FATIMA array served for fast-timing spectroscopy, while GALILEO provided precise energy information. 3. Data analysis The specific isotopes of interest were unambiguously selected by gating on Zand A/Q obtained from the FRS, thus enabling the study of the delayed γ-ray transitions in 96Pd (see Fig. 1). To determine the lifetimes of intermediate states populated in the decay of the 8+isomer, the Eγ–Eγ–∆t correlations were analyzed. Two methods were used to obtain the lifetimes of the 4+and 2+states: a fit of the exponential decay curve to the data, and the Generalized Centroid Difference Method (GCDM) [19]. As shown in Fig. 2(a), the time difference distribution for the 684– 1415 keV coincidence is symmetric, consistent with the expected short lifetime of the 2+state. Using the GCDM (Fig. 2(b)), the upper limit of T1/2≤14 ps was obtained after taking into account the PRD (Prompt Response Distribution) correction. Based on the small lifetime value of the 2+state, the 4+single experimental decay was fitted to the sum of time difference distributions for the 684 keV and 1415 keV transitions with re- 4-A30.4 A. Yaneva et al. Fig. 1. Energy spectrum for isomer-delayed γ-rays obtained from FATIMA correlated to implantation of 96Pd. The known transitions below the 8+isomer were labelled. The other peaks correspond to 139La and 79,81Br neutron-induced γ-rays and background lines. The inset shows the level scheme. Fig. 2. (a), (c) Background-subtracted time difference distributions of γ-rays feeding and depopulating the 2+and 4+states, respectively. The spectrum for the 4+state is a sum of the distributions for two feeder-decay coincidences (see the text). (b), (d) Delayed and anti-delayed time distributions for the 2+and 4+states, respectively [19]. Fast-timing Measurement in 96 Pd: Improved Accuracy . . . 4-A30.5 spect to the 325 keV feeder. The half-life of T1/2= 1.00(5) ns was obtained for the fit to the spectrum (Fig. 2(c)) as well as for the GCDM method (Fig. 2(d)). As preliminarily indicated by Jazrawi et al. [3], the obtained results are consistent with previously published data by Mach et al. (1.0(1) ns and ≤17 ps) [12]. Moreover, in the present analysis, the accuracy of the determined lifetime of the 4+state was increased. 4. Conclusion The half-lives for the yrast 4+and 2+states of 96Pd were measured using a single exponential decay fit to the data and the Generalized Centroid Difference Method. The obtained values are consistent with previously published data for these states. An increased accuracy was achieved for the lifetime of the 4+state. The authors would like to thank the staff of the FRS and the GSI accelerator for their excellent support. The results were obtained in the context of FAIR Phase-0 Darmstadt, Germany. This work was supported by the Swedish Research Council under grants Nos. 621-2014-5558 and 2019-04880. Support by the STFC under grants Nos. ST/G000697/1, ST/P005314, and ST/P003982/1; by the UK Department for Business, Energy and Industrial Strategy via the National Measurement Office; by the BMBF under grants Nos. 05P19RDFN1, 05P21RDFN1, and 05P21RDFN9; by the Helmholtz Research Academy Hesse for FAIR (HFHF); by the GSI F&E grant No. KJOLIE1820; and by BMBF grant 05P19PKFNA are also acknowledged. P.H.R. and R.S. acknowledge support from the National Measurement System program unit of the UK’s Department for BGS. G.H., M.S., and R.L. acknowledge IN2P3-GSI agreements, ADI-IDEX, and CSCUPS grants. L.M.F. acknowledges the Spanish MICINN via project No. RTI 2018-098868-B-100. A.A. acknowledges partial support of the Ministerio de Ciencia e Innovacion grant No. PID2019-104714GB-C21. REFERENCES [1] A.K. Mistry et al.,Nucl. Instrum. Methods Phys. Res. A 1033, 166662 (2022). [2] M. Polettini et al.,Nuovo Cim. C 44, 67 (2021). [3] S. Jazrawi et al.,Radiat. Phys. Chem. 200, 110234 (2022). [4] M. Górska et al.,Physics 4, 364 (2022). [5] T. Faestermann, M. Górska, H. Grawe, Prog. Part. Nucl. Phys. 69, 85 (2013). 4-A30.6 A. Yaneva et al. [6] M. Górska et al.,Z. Phys. A 353, 233 (1995). [7] RISING Collaboration (T. Brock et al.), Phys. Rev. C 82, 061309 (2010). [8] M. Górska et al., «Structure of the heaviest N=Znuclei: Seniority Transitions and EM Transition Rates in 94Pd», GSI, 2019. [9] B. Das et al.,Phys. Rev. C 105, L031304 (2022). [10] B. Das et al., submitted to Phys. Rev. Lett., September 2022. [11] H. Grawe, H. Haas, Phys. Lett. B 120, 63 (1983). [12] H. Mach et al.,Phys. Rev. C 95, 014313 (2017). [13] G. Haefner et al.,Phys. Rev. C 100, 024302 (2019). [14] H. Geissel et al.,Nucl. Instrum. Methods Phys. Res. A 70, 286 (1992). [15] Available: https://edms.cern.ch/ui/file/1865809/2/TDR_HISPEC_ DESPEC_AIDA_public.pdf [16] M. Rudigier et al.,Nucl. Instrum. Methods Phys. Res. A 969, 163967 (2020). [17] A. Goasduff et al.,Nucl. Instrum. Methods Phys. Res. A 1015, 165753 (2021). [18] P.R. John et al., «Assembly of 8 Galileo TC at Institut für Kernphysic TU Darmstadt for the DESPEC Campaign», LNL Annual Report, 2020. [19] J.-M. Regis et al.,Nucl. Instrum. Methods Phys. Res. A 726, 191 (2013).