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 ?

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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