Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 47 (2014)

RIKEN Accel. Prog. Rep. 00 (0)Study of high-spin states in 35 S
S. Go,∗1,∗3 E. Ideguchi,∗2 R. Yokoyama,∗3 M. Kobayashi,∗3 K. Kisamori,∗1,∗3 S. Michimasa,∗3 S. Shimoura,∗3M. Niikura,∗4 A. Yagi,∗5 H. Nishibata,∗5 M. Sugawara,∗6 M. Koizumi,∗7 Y. Toh,∗7 T. Shizuma,∗7 A. Kimura,∗7H. Harada,∗7 K. Furutaka,∗7 S. Nakamura,∗7 F. Kitatani,∗7 Y. Hatsukawa,∗7 D. Suzuki,∗8 I. Matea,∗8D. Verney,∗8 and F. Azaiez∗8measured using the ORGAM array consisting of EUROGAM germanium detectors5) . A total of 13 detectors were installed at 5 diﬀerent angles. The energy
loss of charged particles from compound nuclei wasmeasured by Si-Ball6) , a 4π array of 11 silicon detectors of 170 µm in thickness.
In order to identify high-spin states of 35 S, thegamma–gamma coincidence analysis was performed.
For instance, the transitions reported in the previous study7) were observed by gating the de-excitation
gamma ray from the ﬁrst excited state at 1302 keV of35S (see Fig. 2). All possible energy gates were examined to construct the level scheme. Thus, an 1576-keV
E2 transition from the excited state at 8.8 MeV wasfound. The half-life was estimated to be less than afew hundred femto seconds due to the existence of theresidual Doppler shift of the transition8) . This means
the transition has high-collectivity and indicates superdeformed band member in 35 S. Further analysis isbeing carried out.

Superdeformed rotational bands in the mass 40 region have been discovered in 36 Ar,1) 40 Ar2) and 40 Ca3) .
The occurrence of the superdeformed structure in thisregion is related to the existence of large energy gapsthat are formed between the down-sloping f7/2 andthe up-sloping d3/2 and d5/2 orbitals, as can be seenin the Woods-Saxon single particle diagram in Fig. 1.
The diagram also indicates the superdeformed structure in sulfur isotopes since there is a large energy gap
at Z = 16. The spin-parity of the superdeformed band

[321]1/2

1f 7/2[312]5/2-220

180

heads in odd-mass isotopes could give information
about the orbital that drives the superdeformed structure. Therefore, we performed the in-beam gammaray spectroscopy to search for superdeformed states in35
S at the Tandem-ALTO facility, Institut de physique
Nucléaire d’Orsay.
High-spin states of 35 S were produced by the fusion
evaporation reaction, 26 Mg(18 O, 2α1n)35 S. 18 O beamenergies of 75 and 80 MeV were used. The thicknessof the 26 Mg target was 1 mg/cm2 . Gamma rays were
∗2
∗3
∗4
∗5
∗6
∗7
∗8

0

500

1000

2000

Energy (keV)

2500

2869

1991
1824
1500

3000

3594

100

2284

200

Fig. 1. Woods-Saxon orbitals as a function of thequadrupole deformation parameter β2 . The calculation
was performed by the WSBETA code4) .

∗13002421

4000.62063 2032

[211]1/20.4

1576

β20.2

1228

01302 keV gate

500

1389-0.2[202]5/2[330]1/2

844
9781056-0.4

16868

2s1/2

161007

1d 3/2-8[321]3/2

466-6

20

20732-4-0.6[200]1/222Counts

Proton single-particle levels (MeV)[202]3/2

2803500

4000

Fig. 2. Gamma-ray energy spectrum of 35 S in coincidencewith the 1302 keV transition.

References1) C.E. Svensson et al.: Nucl. Phys. A, 682, 1 (2001).
2) E. Ideguchi et al.: Phys. Lett. B, 686, 18 (2010).
3) E. Ideguchi et al.: Phys. Rev. Lett. 87, 222501 (2001).
4) S. Ćwoik et al.: Comp. Phys. Comm. 46, 379 (1987).
5) C.W. Beausang et al.: Nucl. Instr. Meth. A, 313, 37(1992).
6) T. Kuroyanagi et al.: Nucl. Instr. Meth. A, 316, 211(1999).
7) E. Ideguchi et al.: CNS Ann. Rep. 2009, 23 (2011).
8) B. Cederwall et al.: Nucl. Instr. Meth. A, 354 591(1995).

RIKEN Nishina Center
Research Center for Nuclear Physics, Osaka University
Center for Nuclear Study, University of Tokyo
Department of Physics, University of Tokyo
Department of Physics, Osaka University
Chiba Institute of Technology, Faculty of Information andComputer Science
Japan Atomic Energy Agency
Institut de Physique Nucléaire d’Orsay- 38 -1