Decay and nuclear structure of Np isomer

Asai, Masato  ; Suekawa, Yoshihide*; Higashi, Masato*; Kamada, Hiroki*; Tobe, Teruhisa*; Andreyev, A. N.; Hirose, Kentaro  ; Ito, Yuta   ; Makii, Hiroyuki   ; Nishio, Katsuhisa   ; Niwase, Toshitaka*; Orlandi, R.  ; Sakama, Minoru*; Sato, Tetsuya   ; Shibata, Michihiro*; Suzaki, Fumi  ; Suzuki, Hayato*; Tokoi, Katsuyuki*; Tomitsuka, Tomohiro; Tsukada, Kazuaki  

We have carried out experiments to study nuclear structure of the new isomer Np which we discovered recently. The Np was produced in the reaction of U target with Li beam at JAEA tandem accelerator, and was mass-separated with an on-line isotope separator (ISOL). The half-life was determined accurately through LX-ray measurements. The transition emitted by following the isomeric transition was successfully observed through LX- coincidence measurements. Moreover, the multipolarities of the transitions were determined with internal-conversion electron measurements. On the basis of these experimental results, We have clarified excitation energy, spin-parity, and nuclear structure of Np.