Deartment of Physics;
Dalian University;
Dalian 116622;
China State Key Lab. of Materials Modification by Laser;
Electron and Ion Beams Department of Physics;
Dalian University of Technology;
Dalian 116024;
China;
State Key Lab. of Materials Modification by Laser;
Electron and Ion Beams Department of Physics;
Dalian University of Technology;
Dalian 116024;
China;