1. Department of Physics, Women′s Christian College (Affiliated to Manonmaniam Sundaranar University, Tirunelveli), Nagercoil-629001, India
2. Department of Physics, Malankara Catholic College (Affiliated to Manonmaniam Sundaranar University, Tirunelveli), Kaliakkavilai-629153, India
3. P.G. and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya, College of Arts and Science, Coimbatore-641020, India