Department of Modern Physics;
University of Science and Technology of China;
Hefei 230026;
Department of Physics;
Purdue University;
West Lafayette;
Indiana 47907;
U.S.A.;
Physics Department;
Brookhaven National Laboratory;
Upton;
New York 11973;
U.S.A.;
School of Physical Sciences;
National Institute of Science Education and Research;
Bhubaneswar 751005;
India;