[1] Sri Ramakrishna Engn Coll, Dept Phys, Coimbatore 641022, Tamil Nadu, India
[2] Sri Ramakrishna Engn Coll, Dept Chem, Coimbatore 641022, Tamil Nadu, India
[3] Periyar Univ, Dept Phys, Salem 636011, India
[4] Manonmaniam Sundaranar Univ, Dept Phys, Abhishekapatti 627012, Tirunelveli, India