轻核衰变实验计划 华辉 北京大学物理学院 HIRFL-RIBLL1合作组会议, 近代物理研究所，2013-08-15

一、研究动机

目标核

Large B(E2, 01+(g.s.)  21+) = 541±102 e2fm4 The 34Mg(N=22) nucleus is considered as the heaviest in the “island of inversion”. Low 2+ energy: 660±1 keV Large B(E2, 01+(g.s.)  21+) = 541±102 e2fm4 => strong deformation|2|~ 0.54 [N. Hinohara et al., Phys. Rev. C84, 061302 (2011)] [H. Iwasaki et al., Phys. Lett. B 522, 227 (2001)] [J.A. Church et al., Phys. Rev. C72, 054320 (2005)] [K.Yoneda et al., Phys. Lett. B 499, 233 (2001)]

34Al的研究现状

Gated beta-times spectra 2719 02+ 4 607 Gate on 929 keV : 54.4 (5) ms Gate on 551 keV : 26 (1) ms S. Nummela et al., PRC63(2001)044316 Gated beta-times spectra

?  Experiment modif. SDPF-U-SI 34Al 34Si 4- (Iβ) E3 β − 54% 46% β − 54% ANTOINE modif. SDPF-U-SI 1+ 550 keV 4- 2570 02+ 3510 21+ ~5000 5-,3-,4- 10% 30% (59 ms) 34Al 34Si 0 0g.s.+ (30 ms) <10% >50% (Iβ) 67 11 br.(γ)=46% 4 2719 02+ 3326 21+ (54(1) ms) 61(40) 17(6) 4255 3 (1+) (26(1) ms) 4379 (3-,4-,5-) 4970 (3-,4-,5-)  ? Experiment modif. SDPF-U-SI 5330 (22+)

34Al的1+能级结构 E3 46% β − 54% ANTOINE modif. SDPF-U-SI

可能的衰变纲图 34Mg 2n n 32Al 33Al 34Al T 1/2= 20 (10) ms b-2n Qβ=11.7 MeV Sn = 2470 keV 4- 0 T 1/2= 20 (10) ms 5/2+ 0 4- 657keV n En (MeV) Qβ=11.7 MeV S2n = 8010keV 2n Pn 40% P2n 10% 32Al 1+ 0 b-2n

可能的衰变路径 Qβ(34Mg)=11.7 MeV, Sn(34Al)=2.47 MeV and S2n(34Al)=8.01 MeV. 20(10) ms 34Alg.s. 54.4(5) ms 124 keV;28% 34Alm 26(1) ms 33Al 41.7(2) ms 1941 keV;2.5% 32Al 33.0(2) ms 1941 keV;12% 3042 keV;4.3% 34Si 2.77(2) s 429 keV; 30% 1607 keV; 20% 33Si 6.11(2) s 1847 keV; 75% 416 keV; 3.5% 50%? 0%? 10%? 40%? 26% 74% 91.5% 25?% 75?% 12

可能的带结构 rotational bands build on1/2+[200] build on 3/2-[321] 33Mg New SPIN ASSIGNMENTS Neyens et al., PRL94 (2005) 33Mg 159 705 484 1243 3/2- 2w (5/2) - 2w (3/2+) 1w 546 (1/2)+ 1w (7/2- or 5/2+) 1/2+ 2w (3/2)+ 2w (3/2-) 1w 31Mg 250 ms 16 ns L=1 50 221 461 10.5 ns (7/2-) 1w

34Al S. Nummela,et al, PRC 63,044316(2001) Spectroscopy of 34,35Si by  decay: sd-fp shell gap and single-particle states

二、研究方案 连续束模式下 Thin plastic Si PIN DSSD Veto light particles When a beam particle implants into a pixel of the segmented silicon detector, information is recorded on a computer that helps identify the particle by mass and nuclear charge. In addition, the absolute time of the event is recorded. After some delay, a second event, corresponding to the beta decay of this particle, is detected in or near the same pixel. The energy of the beta particle and the absolute time of the event are recorded. The time difference between implant can be used to extract the beta decay half-life of the nuclear species. DSSD Veto light particles

束流强度估算 Nuclide LISE++ 36Al 0.0054 35Al 2.03 34Al 26.9 35Mg 0.001 34Mg Beam：40Ar, 68.9MeV/u, ~200enA Nuclide LISE++ 36Al 0.0054 35Al 2.03 34Al 26.9 35Mg 0.001 34Mg 0.1406 33Mg 0.8167 33Na 0.0007 32Na 0.0183 31Na 0.227 30Ne 0.0023 29Ne 0.01

Thank you! Peking University