6 pags., 3 figs. -- Open Access funded by  Creative Commons Atribution Licence 4.0. -- Presented at the XXXV Mazurian Lakes Conference on Physics, Piaski, Poland, September 3–9, 2017.Excited states in the neutron-rich isotope 133Sn were studied via the ß decay of 133In. Isomer selective ionization using the ISOLDE RILIS enabled the ß decays of 133Ings (I¿ = 9=2+) and 133mIn (II¿ = 1=2-) to be studied independently for the first time. A description of the experimental setup at the ISOLDE Decay Station is presented together with preliminary results from the experiment.This work was supported in part by the National Science Centre, Poland
(NCN) under contracts No. UMO-2015/18/E/ST2/00217 and No. UMO-
2015/18/M/ST2/00523, by the Spanish MINECO via FPA2015-65035-P
project and by the Portuguese FCT via CERN/FIS-NUC/0004/2015 project.Peer Reviewe

Adamska, E.

Barzakh, A.E.

Benito, J.

Benzoni, G.

Berry, T.

Carmona, M.

Chrysalidis, K.

Correia, G.

Costache, C.

Day Goodacre, T.

Fedorov, D. V.

Fedosseev, V. N.

Fernández-Martínez, G.

Fila, M.

Fraile, Luis M.

Galaviz, D.

García Borge, María José

Grzywacz, R.

Henrich, C.

Illana, A.

Janas, A.

Johnston, K.

Karanyonchev, V.

Kicinska-Habior, M.

Korgul, A.

Lica, R.

Madurga, Miguel

Marroquín, I.

Marsh, B.

Martínez, C.

Mazzocchi, C.

Miernik, K.

Mihai, R.

Olaizola, B.

Paulaskalas, S.

Piersa, M.

Rothe, S.

Régis, J.-M.

Simpson, G.

Sotty, Ch.

Stan, L.

Stanoiu, M.

Stryjczyk, M.

Sánchez-Tembleque, V.

Turturica, A.

Udías, J. M.

Vedia, V.

Villa, A.

Walters, W. B.

Álvarez, R.

Excited states in the neutron-rich isotope Sn-133 were studied via the beta decay of In-133. Isomer selective ionization using the ISOLDE RILIS enabled the beta decays of In-133(gs) (I-pi = 9/2(+)) and In-133m (I-pi = 1/2(-)) to be studied independently for the first time. A description of the experimental setup at the ISOLDE Decay Station is presented together with preliminary results from the experiment

Fraile, L. M.

Alvarez, R.

Barzakh, A. E.

Borge, M. J. G.

Goodacre, T. Day

Fernandez-Martinez, G.

Janas, Z.

Madurga, M.

Marroquin, I.

Martinez, C.

Regis, J-M

Sanchez-Tembleque, V.

Udias, J. M.

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INVESTIGATION OF LOW-LYING STATES IN Sn-133 POPULATED IN THE beta DECAY OF In-133 USING ISOMER-SELECTIVE LASER IONIZATION

Fedorov, D.V.

Fedosseev, V.N.

Lică, R.

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Vol. 49 (2018) ACTA PHYSICA POLONICA B No 3INVESTIGATION OF LOW-LYING STATES IN 133SnPOPULATED IN THE β DECAY OF 133In USINGISOMER-SELECTIVE LASER IONIZATION∗M. Piersaa, A. Korgula, L.M. Fraileb, J. Benitob, E. AdamskaaR. Álvarezc, A.E. Barzakhd, G. Benzonie, T. BerryfM.J.G. Borgeg, M. Carmonab, K. Chrysalidisg, G. CorreiagC. Costacheh, T. Day Goodacreg,i, D.V. FedorovdV.N. Fedosseevg, G. Fernández-Martínezj, M. FilaaD. Galavizk, R. Grzywaczl,m, C. Henrichj, A. Illanan, Z. JanasaK. Johnstong, V. Karanyonchevo, M. Kicińska-HabioraR. Licăg, M. Madurgag, I. Marroquínp, B. MarshgC. Martínezb, C. Mazzocchia, K. Miernika, R. MihaihB. Olaizolaq, S. Paulaskalasl, J.-M. Régiso, S. RothegV. Sánchez-Temblequeb, G. Simpsonr, Ch. Sottyh, L. StanhM. Stănoiuh, M. Stryjczyka,n, A. Turturicah, J.M. UdíasbV. Vediab, A. Villab, W.B. WalterssaFaculty of Physics, University of Warsaw, Warszawa, PolandbGrupo de Física Nuclear, Universidad Complutense de Madrid, CEI Moncloa, Madrid, SpaincEscuela Tecnica Superior de Arquitectura, Universidad Politécnica de Madrid, Madrid, SpaindPetersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, RussiaeINFN — Sezione di Milano, Milano, ItalyfDepartment of Physics, University of Surrey, United KingdomgCERN, Geneva, SwitzerlandhHoria Hulubei National Institute of Physics and Nuclear EngineeringBucharest-Măgurele, RomaniaiSchool of Physics and Astronomy, The University of Manchester, Manchester, United KingdomjInstitut für Kernphysik, Technische Universität Darmstadt, GermanykLIP and Faculty of Sciences, University of Lisbon, PortugallDepartment of Physics and Astronomy, University of Tennessee, Knoxville, USAmPhysics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USAnInstituut voor Kern- an Stralingsfysica, K.U. Leuven, Leuven, BelgiumoInstitut für Kernphysik, Universität zu Köln, Köln, GermanypInstituto de Estructura de la Materia, CSIC, Madrid, SpainqDepartment of Physics, University of Guelph, Guelph, CanadarLPSC, IN2P3 (CNRS), Université Grenoble Alpes, Grenoble, FrancesDepartment of Chemistry, University of Maryland, Maryland, USA(Received December 18, 2017)Excited states in the neutron-rich isotope 133Sn were studied via theβ decay of 133In. Isomer selective ionization using the ISOLDE RILISenabled the β decays of 133Ings (Iπ = 9/2+) and 133mIn (Iπ = 1/2−) to be∗ Presented at the XXXV Mazurian Lakes Conference on Physics, Piaski, Poland,September 3–9, 2017.(523)524 M. Piersa et al.studied independently for the first time. A description of the experimentalsetup at the ISOLDE Decay Station is presented together with preliminaryresults from the experiment.DOI:10.5506/APhysPolB.49.5231. IntroductionIn the last two decades technological advances have allowed new exper-imental studies to extend our knowledge about the neutron-rich nucleus133Sn. This nuclide, having one neutron above the doubly magic 132Sncore, is the main player to deduce neutron single-particle (SP) states aboveN = 82. The first investigation of 133Sn was performed with β-decay spec-troscopy of 134In, for which the large probability of β-delayed neutron emis-sion (Pn = 65% [1]) opens great possibilities to study the states of interestby measuring γ rays in coincidence with delayed neutrons [2, 3]. Thesemeasurements were later followed by reaction studies based on one-neutrontransfer reactions [4–7]. The aforementioned investigations provided mu-tually consistent information about SP energies for νp3/2 (E = 854 keV),νp1/2 (E = 1363 keV), νh9/2 (E = 1591 keV) and νf5/2 (E = 2005 keV)neutron orbitals relative to the νf7/2 ground state of 133Sn. Nevertheless,the question of the position of the neutron unbound νi13/2 state remainsopen for investigation. In addition, recent studies indicate the need to studyhighly-excited states in 133Sn, for which γ-ray emission was found to be adecay mode, competing with β-delayed neutron emission [7].Studies of 133Sn via the β decay of 133In, which were not successfullyperformed so far [2], are a reliable way to provide precise data to clarifythe structure of excited states in 133Sn. The 133In β-decay studies can beperformed not only for the Iπ = (9/2+) ground state (T1/2 = 165(3) ms [8]),but also, independently, for the decay of its Iπ = (1/2−) isomeric level,which has a similar half-life (T1/2 = 180(10) ms [8]).The purpose of this work was to verify the experimental possibilities toinvestigate separately the β decay from the 133In Iπ = (9/2+) ground stateand its Iπ = (1/2−) isomeric level. Since there is a large spin differencefor the two β-decaying states of the parent-nucleus, they are expected topopulate different levels in the daughter nucleus 133Sn.2. ExperimentOur experiment was performed at the Isotope Separator On-Line facility(ISOLDE) [9] at CERN, where 1.4GeV protons from the Proton SynchrotronBooster (PSB) were directed on a uranium carbide target equipped witha neutron converter. Fission products were diffused from the target materialInvestigation of Low-lying States in 133Sn Populated in the β Decay of 133In . . . 525and then effused via a transfer line to the “hot cavity” ion source for ioniza-tion towards the ionizer tube. Ionization of the desired atoms was providedby the Resonance Ionization Laser Ion Source (RILIS) [10]. After extractionand acceleration by an electrostatic potential of 40 kV, ions of 133In weremass separated using the High Resolution Separator (HRS) [11]. Finally,the ion beam was transmitted to the ISOLDE Decay Station (IDS) [12] andimplanted on a movable tape. The collection point was surrounded by fourHPGe clover detectors, two LaBr3(Ce) detectors and a fast-time responseβ detector, which consisted of thin plastic scintillator (1 inch in diameter)coupled to a fast PMT. All signals from the detection system, including theproton timing signal from PSB were recorded and sampled in a triggerlessmode using the Nutaq digital data acquisition system [13]. This enabled theoff-line correlation of the events with the time of the proton pulse impacton the target.Thanks to the RILIS, which not only offers element selectivity but alsoallows for isomer selective ionization for odd-mass In isotopes, the β de-cay of 133In was studied with selective ionization of either 133gIn or 133mIn.The RILIS was applied to ionize indium with an ionization scheme con-sisting of a resonant first excitation step and a non-resonant (NR) ioniz-ing step {λ1|λ2} = {304 nm|532 nmNR} [14, 15]. The resonant transitionwas excited with frequency tripled light from a Titanium:Sapphire (Ti:Sa)laser operated in a “narrowband” mode of operation (fundamental linewidth∼ 800 MHz) [16]. The different hyperfine structures in the atomic energylevels of the Iπ = 9/2+ ground state and the Iπ = 1/2− isomer made itpossible to employ the narrowband Ti:Sa laser for isomer selective ioniza-tion of indium. The RILIS scan was performed with the less exotic beamof 129In. A schematic drawing illustrating the principle of a RILIS scan ispresented in Fig. 1. The number of counts for γ rays that uniquely decayFig. 1. Schematic drawing behind the idea of the online RILIS-IDS scan for 129Inbeam, performed to find optimum laser wavelength providing minimum mixingratio of β-decaying states (see the text for details).526 M. Piersa et al.from Iπ = 9/2+ ground state or Iπ = 1/2− isomeric state of 129In are plot-ted as a function of the wavelength of the narrowband Ti:Sa laser. Theevaluation of the ground state/isomer ion beam composition as a functionof laser wavelength allowed the selection of the optimum laser frequency tostudy the decay from a desired state of the parent nucleus with a minimummixing ratio of ground state versus isomer.3. Results and discussionIn Fig. 2, we present the time-correlated β-gated γ-ray spectra recordedby the HPGe detectors for 133In decay, which were measured independentlyfor the decay of the Iπ = (9/2+) ground state and the Iπ = (1/2−) iso-mer. The total duration of the measurement with selective separation for133In ions in the ground state was 18.5 hours, while for ions in its isomericstate, it lasted for 11.5 hours. We identified γ rays following 133In → 133Sndecay at energies 854 keV and 1561 keV. The 854 keV line was found tobe in β–γ–γ coincidence with the 513 keV transition (Fig. 2). Other tran-133Ing. s.(9/2 +)133mIn (1/2 -)Fig. 2. Portions of the β-gated γ-ray spectra of the 133In decay measured withRILIS set on Iπ = (1/2−) isomeric state (upper part) and Iπ = (9/2+) groundstate (lower part), time-correlated with the proton pulse occurrence. The timegate corresponds to about three half-lives of the ground and isomeric states of133In, respectively [8]. Part of the β-gated γ-ray spectrum in coincidence with the854 keV transition is presented in the upper right corner. Lines marked with a star(∗) are unassigned, while those marked with a cross (+) arise from the neutron-induced activity.Investigation of Low-lying States in 133Sn Populated in the β Decay of 133In . . . 527sitions visible in both spectra belong to daughter activities present in thesubsequent part of the decay chain of 133In. Dominant lines in Fig. 2 arisefrom the 132Sn → 132Sb decay [17]. Apart from that, we identified linescorresponding to neutron-induced activity, mainly due to inelastic neutronscattering reactions with stable germanium isotopes in the detectors [18].The difference in the γ-ray spectra for 133In decay from ground- andisomeric-state can be explained by spin-parity selection rules. Because ofthe large spin difference between these two states, their decay will populatedifferent groups of levels. In the decay of the Iπ = (1/2−) isomeric state,two levels with assigned low-spin values, Iπ = 3/2− (Eγ = 854 keV) andIπ = (1/2−) (Eγ = 513 keV) are fed in the 133Sn daughter nucleus. Itshould be noted that in our spectrum there is no line at 2005 keV, whichwas reported in previous β-decay studies of 133In [2]. Our results confirmprevious observations about low-lying states in 133Sn including consistentinformation about the position of the Iπ = (1/2−) state, observed in theβ decay of 133In for the first time. A partial decay scheme of 133In is pre-sented in Fig. 3. The presence of a very weak 1561 keV line in the γ-rayspectrum of the decay of isomeric Iπ = (1/2−) state is due to a small impu-rity of the beam. When the laser wavelengths were optimized to selectivelyionize 133In atoms in the isomeric state, the ratio of ions in the isomericstate versus those in the ground state was not high enough to completelysuppress the contribution from the decay of the Iπ = (9/2+) ground state.The intensity of the 1561 keV γ ray was used to evaluate the impurity of thebeam originating from the presence of ions in the Iπ = (9/2+) ground state.The ratio of 1561 keV γ-ray intensities registered when RILIS was set on133SnFig. 3. Schematic representation of 133In β decay. The Qβ and Sn values weretaken from [19], T1/2 and energy of Iπ = (1/2−) level in 133In from [8].528 M. Piersa et al.Iπ = (1/2−) versus when on Iπ = (9/2+) was found to be 0.05(1). We donot observe the 854 keV line in the spectrum collected when RILIS was setto separate ions in the Iπ = (9/2+) ground state of 133In, indicating a highbeam purity.4. SummaryLow-lying states in 133Sn were studied in the β decay of 133In at theISOLDE facility. Thanks to the isomer-selective ionization provided byRILIS, we were able for the first time to study separately to study sepa-rately the β decay from the ground- and from the isomeric-state of 133In.The impurities of the beam of 133In ions in these two states were found to benegligible. Our data are consistent with the previous results on the low-lyinglevel structure of 133Sn [2–7], and provide further support for the adoptedspin assignments of low-lying states in 133Sn.This work was supported in part by the National Science Centre, Poland(NCN) under contracts No. UMO-2015/18/E/ST2/00217 and No. UMO-2015/18/M/ST2/00523, by the Spanish MINECO via FPA2015-65035-Pproject and by the Portuguese FCT via CERN/FIS-NUC/0004/2015 project.REFERENCES[1] A.A. Sonzogni, Nucl. Data Sheets 103, 1 (2004).[2] P. Hoff et al., Phys. Rev. Lett. 77, 1020 (1996).[3] P. Hoff et al., Hyperfine Interact. 129, 141 (2000).[4] K.L. Jones et al., Nature (London) 465, 454 (2010).[5] K.L. Jones et al., Phys. Rev. C 84, 034601 (2011).[6] J.M. Allmond et al., Phys. Rev. Lett. 112, 172701 (2014).[7] V. Vaquero et al., Phys. Rev. Lett. 118, 202502 (2017).[8] Yu. Khazov, A. Rodionov, F.G. Kondev, Nucl. Data Sheets 112, 855 (2011).[9] R. Catherall et al., J. Phys. G 44, 094002 (2017).[10] V. Fedosseev et al., J. Phys. G 44, 084006 (2017).[11] E. Kugler et al., Nucl. Instrum. Methods Phys. Res. B 70, 41 (1992).[12] http://isolde-ids.web.cern.ch/isolde-ids/[13] http://nutaq.com[14] M.L. Muchnik et al., Quantum Electron. 13, 1515 (1983).[15] I. Dillmann et al., Eur. Phys. J. A 13, 281 (2002).[16] S. Rothe et al., Nucl. Instrum. Methods Phys. Res. B 317, 561 (2013).[17] H. Mach et al., Phys. Rev. C 51, 500 (1995).[18] T. Siiskonen, H. Toivonen, Nucl. Instrum. Methods Phys. Res. A 540, 403(2005).[19] M. Wang et al., Chin. Phys. C 36, 1603 (2012).

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Investigation of low-lying states in 133sn populated in the - Decay of 133in using isomer-selective laser ionization

Investigation of low-lying states in 133sn populated in the - Decay of 133in using isomer-selective laser ionization

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