Speaker
Atsuko Odahara
(Department of Physics, Osaka University)
Description
We are performing the experimental studies on high-spin isomers [1].
These isomers have been reported in $N$=83 isotones with $Z$=60$-$67.
The spins of these isomers are 49/2$^+$ and 27$^+$ for odd and odd-odd
nuclei, respectively. Their shapes were known to be oblate with a deformation
parameter $\beta$$\sim$$-$0.2. These isomerism were understood to be
caused by the sudden shape change from near spherical to oblate shapes.
The experiments to search for the isomers of the same origin in other isotopes
of $A$$\sim$90 and $A$$\sim$150 near $\beta$-stability line were made
using the secondary beam line, EN course [2] at RCNP, Osaka University.
Although EN course was developed as the fragment mass separator,
experiments using low-energy heavy ion beams have been successfully
performed.
Experiment to search for isomers in nuclei near $A$$\sim$90 based on the
recoil catcher method was carried out using EN course as a recoil mass
separator. Reaction products produced by the fusion reaction of $^{13}$C
+ $^{86}$Kr with the beam energy of 7.4 MeV/u were transported
through $\sim$16m down to a catcher with flight time of $\sim$500ns.
A Ge detector ball which consists of 14 coaxial-type detectors was installed
at the catcher position. Gamma-rays emitted from isomers and daughter nuclei
of the $\beta$ decays were clearly observed.
The RI beam of $^{17}$N was also developed to search for isomers in nuclei
near $A$$\sim$150. The neutron rich RI beam is necessary to produce
high-spin states by the fusion reaction in nuclei near $\beta$-stability line.
The $^{17}$N beam was produced by the $^9$Be($^{18}$O, $^{17}$N)$^{10}$B
reaction with the primary beam energy of 9.1 MeV/u. This secondary beam
of 5.3 MeV/u was separated from the primary $^{18}$O beam and
was transported up to secondary achromatic focal plane. The $^{17}$N
beam intensity was $\sim$10$^4$$\sim$10$^5$ pps.
The recent experimental results obtained by using the secondary beam line
EN course and Ge ball at RCNP will be presented.
[1] A. Odahara, et al., Phys. Rev. {\bf C 72} ( 2005 ) 061303( R ).
[2] S. Mitsuoka et al., Nucl. Inst. and Meth. {\bf A 372} ( 1996 ) 489.
T. Shimoda et al., Nucl. Inst. and Meth. {\bf B 70} ( 1992 ) 320.
Primary author
Atsuko Odahara
(Department of Physics, Osaka University)
Co-authors
Anna Takashima
(Department of Physics, Osaka University)
Eiji Ideguchi
(CNS, University of Tokyo)
Ken-ichiro Kura
(Department of Physics, Osaka University)
Kunihiko Tajiri
(Department of Physics, Osaka University)
Masaki Suga
(Department of Physics, Osaka University)
Masayuki Kazato
(Department of Physics, Osaka University)
Tadashi Shimoda
(Department of Physics, Osaka University)
Tomokazu Suzuki
(Department of Physics, Osaka University)
Tomonori Fukuchi
(RIKEN)
Toshikazu Hori
(Department of Physics, Osaka University)
Toshiyuki Masue
(Department of Physics, Osaka University)
Yasuo Wakabayashi
(CNS, University of Tokyo)
Yasuyuki Gono
(RIKEN)
