1. Department of Physics, Aligarh Muslim University, Aligarh-202002, (U.P.), India
2. Department of Physics, Calicut University, Calicut, (Kerala), India
3. Department of Physics, DSN College, Unnao-209801, (U.P.), India
4. IUC-DAEF, Calcutta Centre, Sector III, Block LB, Plot 8, Salt Lake City, Kolkata-91, India