1. Department of Physics, P.S.R Engineering College, Sevalpatti, Sivakasi 626 140, India
2. Department of Physics, Manonmaniam Sundaranar University, Tirunelveli, India
3. Research Department of Chemistry, Dhanalakshmi College of Engineering, Chennai 601 301, India
4. Department of Physics, Unnamalai Institute of Technology, Kovilpatti 628 503, India