[1] Department of Physics, Bangalore University, Bangalore 560 056, Karnataka, India
[2] Department of Physics, Maharani's Science College for Women, Palace Road, Bangalore 560 001, Karnataka, India
[3] Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu, India
[4] Department of Chemistry, M.S. Ramaiah Institute of Technology, Bangalore 560 054, Karnataka, India