Decays of neutron-rich A ~ 190 nuclei have been studied following projectile fragmentation of a 208Pb beam on a 9Be target at the GSI Fragment Separator. Gamma-ray decays from previously reported isomeric states in 188Ta, 190W and 192, 193Re were used as internal calibrations for the particle identification analysis, together with the identification of previously unreported isomeric decays in 189Ta and 191W. The current work also identifies β-delayed γ rays following the decay of 188Ta to 188W for the first time.Algora, Alejandro, Alejandro.Algora@ific.uv.es ; 

Molina Palacios, Francisco Manuel, Francisco.Molina@ific.uv.es; 

Rubio Barroso, Berta, Berta.Rubio@ific.uv.e

Algora, Alejandro

Alkhomashi, N.

Benlliure, J.

Benzoni, G.

Blazhev, A.

Boutachkov, P.

Bruce, A. M.

Casarejos Ruiz, Enrique

Cullen, I. J.

Cáceres, Lucía

Denis Bacelar, A. M.

Doornenbal, P.

Estévez Aguado, María Esther

Farrelly, G.

Fujita, Y.

Garnsworthy, A. B.

Gelletly, W.

Gerl, J.

Grebosz, J.

Górska, M.

Hoischen, R.

Kojouharov, I.

Kumar, R.

Kurz, N.

Lalkovski, S.

Liu, Z.

Mihai, C.

Molina Palacios, Francisco Gabriel

Mücher, D.

Pietri, S. B.

Podolyák, Zs.

Regan, P. H.

Rubio Barroso, Berta

Schaffner, H.

Steer, S. J.

Tamii, A.

Tashenov, S.

Valiente Dobón, J. J.

Walker, P. M.

Wollersheim, H. J.

Woods, P. J.

Decays of neutron-rich A ~ 190 nuclei have been studied following projectile fragmentation of a 208Pb beam on a 9Be target at the GSI Fragment Separator. Gamma-ray decays from previously reported isomeric states in 188Ta, 190W and 192, 193Re were used as internal calibrations for the particle identification analysis, together with the identification of previously unreported isomeric decays in 189Ta and 191W. The current work also identifies β-delayed γ rays following the decay of 188Ta to 188W for the first time

Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura

Vol. 40 (2009) ACTA PHYSICA POLONICA B No 3β−-DELAYED AND ISOMER SPECTROSCOPY OFNEUTRON-RICH Ta AND W ISOTOPES∗ ∗∗N. Alkhomashia, P.H. Regana, Zs. Podolyáka, S.B. PietriaA.B. Garnsworthya, S.J. Steera, J. Benlliureb, E. Caserejosb, M. GórskacJ. Gerlc, H.J. Wollersheimc, J. Greboszd, N. Kurzc, I. KojouharovcH. Schaffnerc, A. Algorae,p, G. Benzonif , A. Blazhevg, P. BoutachkovcA.M. Bruceh, L. Caceresc, P. Doornenbalc, A.M. Denis BacelarhI.J. Cullena, M.E. Estevezb, G. Farrellya, Y. Fujitai, W. GelletlyaR. Hoischenj, R. Kumark, S. Lalkovskih, Z. Liul, C. Mihaim, F. MolinaeD. Mücherg, B. Rubioe, A. Tamiin, S. Tashenovc, J.J. Valiente-DobónoP.M. Walkera, P.J. WoodslaDepartment of Physics, University of Surrey, Guildford GU2 7XH, UKbUniversidad de Santiago de Compostela, Santiago de Compostela, SpaincGesselschaft für Schwerionenforschung mbH, 64291 Darmstadt, GermanydH. Niewodniczanski Institute of Nuclear Physics PAN, Krakow, PolandeIFIC Valencia, SpainfINFN, Universita degli Studi di Milano, 20133 Milano, ItalygIKP, University of Cologne, 50937 Cologne, GermanyhSchool of Environment and Tech., Univ. of Brighton, Brighton BN2 4GJ, UKiDepartment of Physics, Osaka University, Osaka, JapanjDepartment of Physics, Lund University, 22100 Lund, SwedenkUFAC, New Delhi, IndialUniversity of Edinburgh, UKmNational Inst. for Phys. & Nucl. Engineering, 077125 Magurele, RomanianResearch Center for Nuclear Physics (RCNP), Osaka University, JapanoINFN-Laboratori Nazionali di Legnaro, Padova, ItalypInst. of Nucl. Research of the Hungarian Academy of Sciences, Hungary(Received October 30, 2008)Decays of neutron-rich A ∼ 190 nuclei have been studied following pro-jectile fragmentation of a 208Pb beam on a 9Be target at the GSI FragmentSeparator. Gamma-ray decays from previously reported isomeric states in188Ta, 190W and 192,193Re were used as internal calibrations for the particleidentification analysis, together with the identification of previously unre-ported isomeric decays in 189Ta and 191W. The current work also identifiesβ-delayed γ rays following the decay of 188Ta to 188W for the first time.PACS numbers: 25.70.Mn, 21.60.–n, 29.30.Kv∗ Presented at the Zakopane Conference on Nuclear Physics, September 1–7, 2008,Zakopane, Poland.∗∗ This work is supported by King Abdulaziz City for Science and Technology (KACST),Saudi Arabia; EPSRC/STFC(UK); EURONS, EU contract 506065; The SpanishMinisterio de Educacion y Ciencia; and The German BMBF.(875)876 N. Alkhomashi et al.1. IntroductionLittle spectroscopic information is currently available on the structure ofheavy neutron-rich nuclei with A ∼ 190 due to the difficulties in populatingsuch systems for experimental study. Relativistic-energy projectile fragmen-tation reactions [1,2] can however provide a means by which such nuclei canbe accessed in the laboratory. Structural studies can then be made usingthe high efficiency gamma-ray detection available with the Stopped RISINGgamma-ray spectrometer array [3]. This device enables the measurementof spectroscopic information from the decays of both isomeric states andβ−-delayed decays [4] of ions which have been synthesised in projectile frag-mentation reactions at the GSI facility in Darmstadt, Germany. This shortconference paper presents some preliminary results from β−-delayed γ-rayspectroscopic study of heavy projectile fragments to investigate the low-lyingstates of neutron-rich W isotopes.2. Experimental setupA primary beam of 208Pb at an energy of 1 GeV/nucleon from the SIS-18synchrotron at GSI was fragmented on a 2.45 g/cm2 Be target with the re-sulting ions being separated and identified using the GSI Fragment Separator(FRS) [5]. Two MUlti Sampling Ionization Chamber detectors were used atthe final focal plane of the FRS to measure the energy loss of the individualions. This, together with the time-of-flight of the ions enabled an event-by-event particle identification for the ions transmitted through the FRS. Theions of interest were brought to rest at the end of the FRS in an array of three5 cm × 5 cm × 1 mm Double-Sided Silicon Strip Detectors (DSSSDs) eachsegmented into 16 strips in both the horizontal and vertical directions [4].The DSSSDs used logarithmic preamplifiers [6] to enable the measurementof both the total implantation energy and the energy deposited by the subse-quent β− particle for each decay event for each pixel. This was used to de-termine the implantation positions of the transmitted secondary ions andcorrelate them with their subsequent β-decay signals in the same or neigh-bouring pixels of the DSSSDs. Coincident γ-rays following either isomericdecays or β-delayed emission were measured using the 15 germanium clusterdetectors of the RISING γ-ray array [3].3. Experimental results and summaryThe fragment particle identification was achieved by creating standardtwo dimensional spectra of the energy loss in the MUSIC chamber detector(which is related to the atomic number, Z, of the ions) versus the time-of-flight, TOF (which is related to the mass-over-charge ratio of the transmittedions), on an event-by-event basis for each ion. Reference [5] provides moredetails on the particle identification used in the current work.β−-Delayed and Isomer Spectroscopy of Neutron-Rich Ta and W Isotopes 877Fig. 1 shows gamma-ray spectra associated with decays from previouslyreported [2] isomeric states in 188Ta, 190W and 192,193Re as observed in thepresent work. These isomers were used as checks for the particle identifica-tion analysis and provided an independent validation for the γ-ray energyand timing setups. Decays from two previously unreported isomers were ob-served associated with the 189Ta and 191W nuclei. Fig. 2 shows the β-delayedgamma-ray spectra for 188W following decays from the parent nucleus 188Ta.The γ-ray transitions observed in 188W have been reported previously fromin-beam studies using deep-inelastic [7] and two-neutron transfer reactions[8]. Three discrete transitions were identified at energies of 143, 297 and434 keV. These correspond to the decays from the yrast 2+, 4+ and 6+states, respectively. The transition from the previously identified [8] yrast8+ state (Eγ = 554 keV) is not observed here, suggesting that the β− de-caying state has a tentative spin of (I = 5).Fig. 1. Gamma-ray energy and decay time spectra for decays from isomeric statesobserved in the current work.In conclusion, the RISING active stopper has been used to obtain spec-troscopic information on heavy neutron-rich nuclei around A ∼ 190 whichwere populated following projectile fragmentation reactions using a 1 GeVper nucleon, 208Pb primary beam. Isomeric and β-delayed γ-ray spec-troscopy have both been used to provide new spectral information on the878 N. Alkhomashi et al.Fig. 2. Beta-delayed γ-ray spectrum following decay events associated with 188Taprimary fragments which populate 188W. A time condition that the β-particle mustbe measured within 120 seconds of the secondary beam implant in the active stop-per has been applied to this spectrum. The inset shows the decay time spec-trum associated with this decay half-life obtained by projecting the decay times ofβ-delayed gamma-ray coincidence events relative to the 188Ta implantation time.low-lying internal states in Ta and W nuclei. The spectra for the β−-decayof 188Ta show the previously reported γ rays associated with decays of levelsin the 188W daughter nucleus up to a spin-parity of 6+. Data on heavierTa → W decays, which were studied in the same experiment, are currentlyunder analysis and the preliminary results are reported elsewhere [4].REFERENCES[1] J. Benlliure et al., Nucl. Phys. A660, 87 (1999).[2] M. Caamano et al., Eur. Phys. J. A23, 201 (2005).[3] S. Pietri et al., Nucl. Instrum. Methods Phys. Res. B261, 1079 (2007).[4] P.H. Regan et al., Int. J. Mod. Phys. E, in press.[5] H. Geissel et al., Nucl. Instrum. Methods Phys. Res. B70, 286 (1992).[6] R. Kumar et al., Nucl. Instrum. Methods Phys. Res. A598, 754 (2009).[7] Zs. Podolyák et al., Int. J. Mod. Phys. E13, 123 (2004).[8] T. Shizuma et al., Eur. Phys. J. A30, 391 (2006).

β-Delayed and isomer spectroscopy of neutron-rich Ta and W isotopes

Alkhomashi, N

Regan, PH

Podoyak, Z

Pietri, SB

Garnsworthy, AB

Steer, SJ

Benlliure, J

Caserejos, E

Gorska, M

Gerl, J

Wollersheim, HJ

Grebosz, J

Kurz, N

Kojouharov, I

Schaffner, H

Alcora, A

Benzoni, G

Blazhev, A

Boutachkov, P

Bruce, AM

Caceres, L

Doornenbal, P

Bacelar, AMD

Cullen, IJ

Estevez, ME

Farrelly, G

Fujita, Y

Gelletly, W

Hoischen, R

Kumar, R

Lalkovski, S

Liu, Z

Mihai, C

Molina, F

Muecher, D

Rubio, B

Tamii, A

Tashenov, S

Valiente-Dobon, JJ

Walker, PM

Woods, PJ

University of Surrey

English

beta(-)-DELAYED AND ISOMER SPECTROSCOPY OF NEUTRON-RICH Ta AND W ISOTOPES

Alkhomashi, N

Regan, PH

Podoyak, Z

Pietri, SB

Garnsworthy, AB

Steer, SJ

Benlliure, J

Caserejos, E

Gorska, M

Gerl, J

Wollersheim, HJ

Grebosz, J

Kurz, N

Kojouharov, I

Schaffner, H

Alcora, A

Benzoni, G

Blazhev, A

Boutachkov, P

Bruce, AM

Caceres, L

Doornenbal, P

Bacelar, AMD

Cullen, IJ

Estevez, ME

Farrelly, G

Fujita, Y

Gelletly, W

Hoischen, R

Kumar, R

Lalkovski, S

Liu, Z

Mihai, C

Molina, F

Muecher, D

Rubio, B

Tamii, A

Tashenov, S

Valiente-Dobon, JJ

Walker, PM

Woods, PJ

Surrey Research Insight

Decays of neutron-rich A similar to 190 nuclei have been studied following projectile fragmentation of a Pb-208 beam on a Be-9 target at the GSI Fragment Separator. Gamma-ray decays from previously reported isomeric states in Ta-188, W-190 and (192,193) Re were used as internal calibrations for the particle identification analysis, together with the identification of previously unreported isomeric decays in Ta-189 and W-191. The current work also identifies beta-delayed gamma rays following the decay of Ta-188 to W-188 for the first time

β-Delayed and isomer spectroscopy of neutron-rich Ta and W isotopes

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