1. 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，

2. 一、研究动机

3. 目标核

4. 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, (2011)]
[H. Iwasaki et al., Phys. Lett. B 522, 227 (2001)]
[J.A. Church et al., Phys. Rev. C72, (2005)]
[K.Yoneda et al., Phys. Lett. B 499, 233 (2001)]

5. 34Al的研究现状

7. Gated beta-times spectra 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

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

9. 34Al的1+能级结构 E3
46%
β − 54%
ANTOINE
modif. SDPF-U-SI

10. 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
keV n
En (MeV)
Qβ=11.7 MeV
S2n = 8010keV 2n
Pn 40%
P2n 10%
32Al
1+ 0
b-2n

12. 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

13. 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

14. 34Al
S. Nummela,et al, PRC 63,044316(2001) Spectroscopy of 34,35Si by  decay: sd-fp shell gap and single-particle states

15. 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

17. 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

18. Thank you!
Peking University