1. Department of Physics, Jadavpur University, Jadavpur, Kolkata-700032, India
2. Department of Physics, Lady Brabourne College, Kolkata-700017, India
3. Department of Physics, Haldia Government College, Haldia, Purba Medinipur-721657, India
4. Department of Studies in Chemistry, Central College Campus, Bangalore University, Bangalore-560001, India
5. Department of Physics, Jadavpur University, Jadavpur, Kolkata-700032, India , Tel.: +919331041417, Fax: 033 24138917