1. Department of Physics, Ramakrishna Mission Vivekananda University, P.O. Belur Math, Howrah 711202, India
2. Department of Physics, Acharya Prafulla Chandra College, New Barrackpore, Kolkata 700131, India
3. Indian Institute Astrophysics, Bangalore 560034, India
4. Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India