1. Department of Physics, Jadavpur University, 188, Raja S.C. Mallick Rd, Kolkata 700032, India
2. Department of Physics, Sammilani Mahavidyalaya, Baghajatin Station, E. M. Bypass, Kolkata 700094, India
3. Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India