[1] Southeast Univ, Sch Phys, Nanjing 211189, Peoples R China
[2] NYU, Dept Phys, New York, NY 10003 USA
[3] Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08854 USA
[4] NIST, NIST Ctr Neutron Res, 100 Bur Dr, Gaithersburg, MD 20899 USA
[5] Univ Maryland, Quantum Mat Ctr, Dept Phys, College Pk, MD 20742 USA
[6] Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA