RIKEN Accel. Prog. Rep. 47 (2014)

HIGHLIGHTS OF THE YEAR

Production cross section measurements of radioactive isotopes byBigRIPS separator at RIKEN RI Beam Factory†
H. Suzuki,∗1 T. Kubo,∗1 N. Fukuda,∗1 N. Inabe,∗1 D. Kameda,∗1 H. Takeda,∗1 K. Yoshida,∗1 K. Kusaka,∗1Y. Yanagisawa,∗1 M. Ohtake,∗1 H. Sato,∗1 Y. Shimizu,∗1 H. Baba,∗1 M. Kurokawa,∗1 T. Ohnishi,∗1 K. Tanaka,∗1O. B. Tarasov,∗1,∗2 D. Bazin,∗1,∗2 D. J. Morrissey,∗1,∗2 B. M. Sherrill,∗1,∗2 K. Ieki,∗1,∗3 D. Murai,∗1,∗3N. Iwasa,∗1,∗4 A. Chiba,∗1,∗4 Y. Ohkoda,∗1,∗4 E. Ideguchi,∗5 S. Go,∗1,∗6 R. Yokoyama,∗6 T. Fujii,∗6D. Nishimura,∗1,∗7 H. Nishibata,∗1,∗8 S. Momota,∗1,∗9 M. Lewitowicz,∗10 G. DeFrance,∗10 I. Celikovic,∗10 andK. Steiger∗1146

We have measured the production rates and production cross sections for a variety of radioactive isotopes which were produced from 124 Xe, 48 Ca, and 238 U
beams at an energy of 345 MeV/nucleon using the BigRIPS separator1).
Proton-rich isotopes with atomic numbers Z = 4052 were produced by projectile fragmentation of the124
Xe beam on a Be target, during which we also measured their momentum distributions. We found thatthe exponential tails at the low-momentum region fall
off faster than those of the LISE++2) calculation withthe original parameterization. The EPAX3.01 crosssection formula3) agreed fairly well with the experimental cross sections. Furthermore, we have discovered four new isotopes on the proton-drip line, 85,86 Ru
and 81,82 Mo. Figure 1 (a) shows a two-dimensional plotof Z versus mass-to-charge ratio (A/Q) in the 85 Ru setting. The four new isotopes were clearly identified on
the left side of the solid lines, which indicate the limits of known isotopes. In the 105 Te setting, 103 Sb was
not observed in our measurement, as shown in Fig. 1(b). We obtained clear evidence that 103 Sb is particleunbound with a half-life upper limit of 49 ns.
Neutron-rich isotopes with Z = 5-16 were producedby the projectile fragmentation of the 48 Ca beam on
Be targets. The EPAX2.15 formula4) reproduces theexperimental cross sections fairly well.
Neutron-rich isotopes with Z = 20-59 were produced
by in-flight fission of a 238 U beam on Be and Pb targets. The measured production rates were comparedwith the LISE++ calculations, in which the abrasion
fission (AF) model and the AF + Coulomb fission
model were used for the 238 U+Be and 238 U+Pb cases,

new

45
4485

Ru

43known

(a)

86

Ru

Z 42
4181

Mo 82
Mo40
39
38
1.9 1.92 1.94 1.96 1.98 2 2.02 2.04
A/Q
54
newknown
52(b)

103

Sb50
Z 48
46
44
1.9

1.95

22.05
A/Q

2.1

2.15

2.2Fig. 1. (a)Enlarged two-dimensional PID plot of Z vs.
A/Q for 85 Ru setting. 85,86 Ru and 81,82 Mo are the newisotopes. (b)PID plot for 105 Te setting.

respectively. In the former case, the LISE++ calculations reproduced the experimental production rates
well for the Z < 50 region but underestimated themfor Z > 50. In the latter case, the LISE++ predictions
reproduce them fairly well overall.

†Condensed from the article in Nucl. Instrum. Meth. Phys.
Res., B 317, 756 (2013)∗1 RIKEN Nishina Center∗2 National Superconducting Cyclotron Laboratory, Michigan
State University∗3 Department of Physics, Rikkyo University∗4 Department of Physics, Tohoku University∗5 Research Center for Nuclear Physics, Osaka University∗6 Center for Nuclear Study, University of Tokyo∗7 Department of Physics, Tokyo University of Science∗8 Department of Physics, Osaka University∗9 School of Environmental Science and Engineering, Kochi
University of Technology∗10 Grand Accelerateur National d’Ions Lourds∗11 Physik Department, Technische Universität MünchenReferences
1) T. Kubo et al.: Nucl. Instrum. Meth. Phys. Res. B 204,
97 (2003).
2) O.B.Tarasov and D.Bazin: LISE++ site, http://lise.nscl.edu,Michigan State University.
3) K. Sümmer: Phys. Rev. C 86, 014601 (2012).
4) K. Sümmer and B. Blank: Phys. Rev. C 61, 034607(2000).

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