1. Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
2. Department of Physics, M. G. Mahavidyalaya, Bhupatinagar, Midnapore (East), West Bengal 721 425, India
3. Department of Chemistry, A. B. N. Seal College, Coochbehar 736101, W.B., India
4. Department of Physics, Behala College, Parnasree, Kolkata-700060, India