1. Department of Physics; Institute of Science; Banaras Hindu University; Varanasi 221005 India
2. School of Mathematical and Physical Sciences (MPS); Dr. Harisingh Gour University; Sagar 470003 India
3. Department of Physics; Indian Institute of Sciences; Banagalore 560012 India
4. Department of Chemistry; Institute of Science; Banaras Hindu University; Varanasi 221005 India