1 / 21

a decay above 100 Sn: 109 Xe, 105 Te and 109 I

a decay above 100 Sn: 109 Xe, 105 Te and 109 I.

sherri
Download Presentation

a decay above 100 Sn: 109 Xe, 105 Te and 109 I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. a decay above 100Sn: 109Xe, 105Te and 109I S.N. Liddick1,2, R.Grzywacz2,3, C.Mazzocchi3, R.D.Page4, K.P.Rykaczewski3, J.C.Batchelder1,C.R.Bingham2,3,I.G.Darby4,G.Drafta2,C.Goodin5, C.J.Gross3, J.H. Hamilton5, A.A.Hecht6,J.K.Hwang5, S.Ilyushkin7,D.T.Joss4,A.Korgul2,5,8,9, W.Krolas9,10, K.Lagergren9,K.Li5, D.Simpson2,11, M.N.Tantawy2, J.Thompson4, J.A.Winger1,7,9 1 UNIversity Radioactive Ion Beam Consortium 2 Department of Physics and Astronomy, University of Tennessee 3 Physics Division, Oak Ridge National Laboratory 4 Department of Physics, University of Liverpool 5 Department of Physics and Astronomy, Vanderbilt University 6 Department of Physics, University of Maryland 7 Department of Physics, Mississippi State University 8 Institute of Experimental Physics, Warsaw University 9 Joint Institute for Heavy-Ion Reactions, Oak Ridge 10 Institute of Nuclear Physics, Polish Academy of Sciences 11 East Tennessee Technical University

  2. a-decay near proton and neutron shell closures N=126 N=82 Z=82 N=50 Z Z=50 N an island of a-radioactivity above proton-rich Sn isotopes due to the Z=50and N=50shell closures

  3. N=Z Search for new alpha emitters above 100Sn: 109Xe, 105Te, 109I • fine structure in alpha decay:→ single particle levels • mass measurements • rp-process termination • nucleons (both protons and neutrons) in d5/2 and g7/2 orbitals: → proton-neutron correlations → superallowed alpha decay [Macfarlane65] 109Xe CN 112Xe* 109I 109I 105Te 105Sb 101Sn Z=50 N=50

  4. 100 ms ba< 0.5 % [Page et al., PRL49 (1994)] 109I a decay and 105Sb 109I Qp=820 keV bp=100% p 1.12 s [Faestermann et al., PLB137 (1984)] p 105Sb Qp=483 keV < 1% 108Te [Tighe et al, PRC49 (1994)] Qa = 3445 keV ba~50%[Schardt et al., NPA326 (1979)] 109I 109I 104Sn 108Te 105Sb Z=50 104Sn N=50

  5. Termination of the astrophysical rp-process • Alpha decay above 100Sn leads to the termination of the rp-process. • Shifting masses / proton separation energies could affect the direction of the rp-process to more exotic nuclei. 109I 105Sb Z=50 N=50 Schatz et al, PRL 86, 3471 (2001)

  6. HRIBF

  7. Fusion-evaporation reactions 54Fe(58Ni,3n)109Xe ~8 part.nA • Recoil Mass Spectrometer used to separated out reaction products based on A/Q.

  8. Excitation function of 110Xe and 109Xe:HIVAP vs experiment Test run (RIB000) preliminary

  9. 109 109/28+ 109/29+ LARGEMCP SMALLMCP DSSD 40 x 40 strips 109/29+ 109/28+ 1600 pixels

  10. Double-sided Silicon Strip Detector • DSSD implantation detector + SiBox and SiLi. • Centerpiece of system is DSSD. • 4 cm x 4 cm segmented into 40 1-mm strips on front and back for a total of 1600 pixels. • 60 um thick. • Implanted ions and subsequent decay events are recorded on an event-by-event basis.

  11. Thick Si(Li) and Four Si detectors around the DSSD (UTK,Mississippi,Vanderbilt contributed) 5 cm • DSSD surrounded by four Si detectors used to reduce background from decay events that are not fully stopped in the DSSD. • Behind DSSD is a thick SiLi detector also for use as a veto.

  12. Digital Electronics • DSP-based data acquisition system (UT/ORNL/UNIRIB):→ recording pulse shapes(traces) for single  and pile-up -  decay events (109Xe 105Te 101Sn)→ method veryselective (identify 100 events among 4.4*108 implanted ions and 1.7*107 decays).,→very sensitive(DT between two pile-up traces covers wide range) very small dead time(<15% at ~3 kHz ions and ~150 Hz traces)

  13. 109Xe

  14. New Acquisition Mode • New acquisition mode developed in order to record microsecond105Te activity after millisecond109Xe activity. • For signals greater than a predetermined threshold, only energy and time recorded. • All others, trace with a length of 25 ms obtained for offline analysis.

  15. 109Xe →105Te →101Sn Example ofa-apile-up traces Back Strip Front Strip 105Te 109Xe 0.275ms

  16. Alpha energy spectra • A energy spectra for those events identified after a 109Xe or 105Te decay. • Fine structure observed in the a decay of 109Xe. • Place excited state in 105Te at an energy of 150 keV. • Only one transition observed in 105Te. 3.918 MeV 4.062 MeV 4.703 MeV

  17. 109Xe,105Te time distributions • Time distributions for 105Te and 109Xe on a logarithmic time axis. • Half-lives fit using the method of Schmidt et al. [1] and result in 620  70 ns and 13  2 ms for decay of 105Te and 109Xe, respectively. • Time distribution cut off at low times in 105Te decay due to software limitations on the identification of an event as a double pulse. 620 [1] K.-H. Schmidt et al., Z. Phys A, 316, 19 (1984)

  18. 109Xe →105Te →101Sn Ea = 3.918 MeV ba = 30% (7/2+) 132 ms 109Xe55 54 l=0 l=2 (7/2+) 0.15 MeV Ea = 4.062 MeV ba = 70% (5/2+) 620  70 ns 105Te53 52 l=0 Ratio of half-lives: 1:20000 Ea = 4.703 keV ba= 100% (5/2+) 1.9 s 101Sn51 50

  19. Systematics of 7/2+ and 5/2+ levels • In a simple single-particle shell model, energy separation between nd5/2 and ng7/2 can be estimated from levels in 101Sn to be ~160 keV. • Systematics of 7/2+ level break at N = 53. • 7/2+ level in 101Sn can be speculated to be ~160 keV.

  20. 109I

  21. Summary • Observation of 109Xe fine structure with first excited state at 150 keV. • Measurement of 109I alpha decay branch and infer the proton separation energy in 105Sb. Looking forward • Search for fine structure in 105Te alpha decay to 101Sn and identification of nd5/2 and ng7/2 energy separation in 101Sn. • Discover 108Xe →104Te →100Sn alpha decay chain: best case for superallowed alpha decay.

More Related