[1] TKM Coll Arts & Sci, Dept Phys, Kollam 691005, Kerala, India
[2] Fatima Mata Natl Coll, Dept Phys, Kollam 691001, Kerala, India
[3] MES Ponnani Coll, Dept Phys, Malappuram, Kerala, India
[4] Mar Thoma Coll, Dept Phys, Thiruvalla 689103, Kerala, India
[5] BCDA Coll Pharm, Kolkata 700127, W Bengal, India
[6] N Bengal Univ, Dept Chem, Siliguri 734013, W Bengal, India
[7] Univ Antwerp, Dept Chem, B-2610 Antwerp, Belgium