1. Department
of Physics, Sammilani Mahavidyalaya, E.M. Bypass, Baghajatin Station, Kolkata 700 075, India
2. Integrated Center for Sciences, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566,
Japan
3. Department
of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032,
India