Nuclear orientation in fusion and synthesis of heavy element at sub-barrier energy

Nishio, Katsuhisa   ; Ikezoe, Hiroshi; Hofmann, S.*; Ackermann, D.*; Antalic, S.*; Aritomo, Yoshihiro; Comas, V. F.*; Dllmann, Ch. E.*; Gorshkov, A.*; Graeger, R.*; Heinz, S.*; Heredia, J. A.*; Heberger, F. P.*; Hirose, Kentaro*; Khuyagbaatar, J.*; Kindler, B.*; Kojouharov, I.*; Lommel, B.*; Makii, Hiroyuki   ; Mann, R.*; Mitsuoka, Shinichi; Nagame, Yuichiro ; Nishinaka, Ichiro; Otsuki, Tsutomu*; Popeko, A. G.*; Saro, S.*; Schdel, M.*; Trler, A.*; Wakabayashi, Yasuo; Watanabe, Yutaka*; Yakushev, A.*; Yeremin, A.*

In-beam measurement of fission-fragment mass distributions in S + U were performed to obtain information on the fusion probability at various orientations of the deformed target nucleus. The experiment was carried out at the JAEA tandem facility. The distributions changed from symmetry to asymmetry when the beam energy was changed from above-barrier to sub-barrier values, indicating the orientation effects on fusion and/or quasifission. We also produced evaporation residues (ERs) as a direct evidence for fusion. The experiment was carried out at GSI by using the velocity filter SHIP. At above-barrier energy, the isotope Hs (5n) was produced and the cross section of 1.8 pb was obtained. It was concluded that the distribution of symmetric mass fragments originate not only from fusion fission, but has a strong component from quasifission. At sub-barrier energy, we produced a new isotope Hs (4n) with the cross section 0.54 pb. We obtained the fusion probability enough to produce SHN. These results were supported by a calculation based on a dynamical description using Langevin equation, where fusion and quasifission were separately determined. The effects of projectile mass (charge) on fusion from the measured fission properties of Si, P, S, Ar, Ca + U are obtained.