Proton and Two-Proton Decay of a High-Spin Isomer in 94 Ag

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Proton and Two-Proton Decay of a High-Spin Isomer in 94 Ag. Ernst ROECKL GSI Darmstadt and Warsaw University. Experimental Techniques. Fusion-evaporation reactions 58 Ni( 40 Ca,p3n) 94 Ag Isotope separation on-line Detectors: Silicon strip detectors: ß particles, protons - PowerPoint PPT Presentation

Text of Proton and Two-Proton Decay of a High-Spin Isomer in 94 Ag

  • Proton and Two-Proton Decayof a High-Spin Isomer in 94AgErnst ROECKLGSI Darmstadt and Warsaw University

  • Fusion-evaporation reactions 58Ni(40Ca,p3n)94AgIsotope separation on-lineDetectors:Silicon strip detectors: particles, protonsGermanium detectors: rays Experimental Techniques

  • Properties of the (21+) isomer of 94Agdeduced from - and -proton studiesE* = 6.7(5) MeVT1/2 = 0.39(4) sfusion-evaporation = 350 pb *) *) Further parameters characterizing the experiment: 40Ca intensity 75 particle-nA, 58Ni-target thickness 3 mg/cm2, ion-source efficiency 10%, intensity of the 94Ag (21+) beam 10 atoms/min, measuring time 80 h I = (21+)C. Plettner et al., Nucl. Phys. A 733, 20 (2004)I. Mukha et al., Phys. Rev. C 70, 044311 (2004)

  • (21+) isomer in 94Ag: What was known by end of 2003Population 0+ ground-state of 94Ag (T1/2 ~ 29 ms, A. Stolz, Ph D Thesis (2000)): not observed in fusion-evaporation reactions !Comparison with shell-model predictions (up to 4p-4h excitations): inversion of 17+ and 21+ levels in 94Ag !0.39(4) s0.61(2) sBeta and -delayed proton emission studied by using a multiple -ray trigger !N=Z=47

  • One-proton decay of the (21+) isomer of 94Ag Search by measuring coincidences between charged particles and - cascades in 93PdExperiment:I. Mukha et al., Phys. Rev. Lett. 95, 022501 (2005)Theory:WKB estimate of protonwidths la Gamow

  • Si-- coincidence, gates on 93Pd lines *)Si singles spectrumscaled down by afactor 2401.01(3) MeV0.79(3) MeV*) 93Pd -rays identified by C. Rusu et al., Phys. Rev. C 69, 024307 (2004)

  • Data on the one-proton decayof the (21+) isomer of 94Ag Ep (MeV)

    ______

    0.79(3)

    1.01(3)Intensityper 100 decays_______

    1.9(3)

    2.2(4) T1/2(exp)(s)

    ______

    21(6)

    18(4)L

    ___

    (4)

    (3,5)T1/2(WKB) /T1/2(exp)

    _______________

    110-6 (L=4)

    310-7 (L=5)Deformation effect? Ii If

    __________

    (21+) (33/2+)

    (21+) (33/2,35/2)

  • Two-proton decay of the (21+) isomer of 94Ag Search by measuring coincidences between charged particles and - cascades in 92RhExperiment:I. Mukha et al., accepted for publication in NatureTheory:Three-body breakup model,L. Grigorenko et al., Phys.Rev. C 68, 054005 (2003)

  • Si-Si-- coincidence, gates shifted offthe 92Rh linesSi-Si-- coincidence, gates on 92Rh lines *)*) 92Rh -rays identified by D. Kastet al., Z. Phys. 356, 363 (1997) 1.88(9) MeV

  • Experimental data on the two-proton decayof the (21+) isomer of 94Ag E2p = 1.88(9) MeV and correlation data ...I = 0.5(3) % per decayT1/2 = 0.39(4)/0.5(3)% = 80(50) sIi If : (21+) (13+,15+)L = (6,8)

  • Relative energy spectra ...Predictions of thebreak-up modelExperimentExpected for sequential 2p decay for proton-protoncorrelations for proton-92RhcorrelationsExpected for isotropic 2p decay

  • Di-proton (2He) emissiona = (long-to-short axis ratio)-1/2Simultaneous emissionof 2 protonsSimultaneous emissionof 2 protons

  • Summary and OutlookThe proton decay of the (21+) isomer of 94Ag has unprecedented features including discovery of one- and two-proton radioactivity from one and the same nuclear state, unambiguous identification of one- and two-proton by measuring coincidences with characteristic rays, new kind of emission of protons from the poles of a prolate-deformed nucleus, tentatively deduced from correlation data.It is mandatory to try to improve the proton-proton correlation data with respect to statistics and angular resolution: Where can such a measurement be done ?

  • if you want to see the field of exotic-beam researchin full glory, please feel invited to the following reading

    The Euroschool Lectures on Physics with Exotic Beams, Vol. 1Lecture Notes in Physics Vol. 651 (2004), J. Al-Khalili and E. R. (Eds.)

    Table of Contents: The Why and How... (M. Huyse), Practioners Shell Model (H.Grawe), Halo Nuclei (J. Al-Khalili), In-flight Separation (D.J. Morrissey, B.R. Sherrill), Stored Exotic nuclei (F. Bosch) Precision Weak-interaction Studies (N. Severjins), Nuclear Astrophysics (K. Langanke, F.-K. Thielemann, M. Wiescher), Medical Applications of Accelerated Ions (W. Kraft-Weyrather)

    www.springeronline.com/3-540-22399-1

  • Si-Si-- coincidence, gates on 93Pd lines *)Singles spectrum scaleddown by a factor 2401.01(3) MeV0.79(3) MeV gateAll spectra gated by 93Pd - rays *)*) 93Pd -rays identified by C. Rusu et al., Phys. Rev. C 69, 024307 (2004)

  • L=(4)L=(3,5)

  • 1.4 - 1.6 MeV1.8 - 1.95 MeVESi1+ ESi2 gates:Si-Si-- coincidence, gates shifted offthe 92Rh linesSi-Si-- coincidence, gates on 92Rh lines *)1.88(9) MeV92Rh94Pd*) 92Rh -rays identified by D. Kastet al., Z. Phys. 356, 363 (1997)

  • This workEstimated by extrapolatingsystematical trends(G. Audi et al., Nucl. Phys.A 729, 337 (2003))

  • What this talk is about1. In the odd-odd nucleus 94Ag an isomer has been observed to have the following unique properties:excitation energy of 6.7 MeV,tentative spin/parity assignment of (21+),half-life of 0.4 s,one-proton and two-proton radioactivity

    2. The one-proton decay is strongly hindered. 3. The two-proton decay is strongly enhanced.

  • Array of three silicon-strip detectors High resolution and low energy-threshold for detecting charged particles (positrons, protons) High granularity*) position information I. Mukha et al., Nucl. Phys. A 745, 9285 (2004) *) Only 2 segments per detector used in this work

  • High resolution and low energy-threshold for detecting particles and protons High granularity position information

    I. Mukha et al., Nucl. Phys. A 745, 9285 (2004)

    Silicon-strip detectors for recording positrons