1. Department of Physics, The American College, Madurai 625 002, India
2. PG and Research Department of Physics, Government Arts College, Melur 625 106, Madurai, India
3. Department of Chemical Engineering, College of Engineering, Kyung Hee University, 1732 Deogyeong-daero, Gihung, Yongin, Gyeonggi 446-701, South Korea