*Nguyen Tien Son1, Pontus Stenberg1, Valdas Jokubavicius1, Hiroshi Abe2, Takeshi Ohshima2, Jawad Ul-Hassan1, Ivan Gueorguiev Ivanov1
(1. Department of Physics, Chemistry and Biology, Linköping Univ., SE-58183 Linköping(Sweden), 2. National Inst. for Quantum and Radiological Sci. and Tech., 1233 Watanuki, Takasaki, Gunma 370-1292(Japan))