1. Department of Physics, Victoria Institution (College), 78 B, A. P. C. Road, Kolkata-700009, India
2. Department of Physics, Sammilani Mahavidyalaya, Baghajatin Station, E.M. Bypass, Kolkata-700075, India
3. Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700 032, India