1. Department of Physics, Hemvati Nandan Bahuguna Garhwal University, Badshahi Thaul Campus, Tehri Garhwal 249 199, India (Corresponding author), e-mail: rcramola@gmail.com, https://orcid.org/0000-0003-0948-0461
2. Department of Physics, Hemvati Nandan Bahuguna Garhwal University, Badshahi Thaul Campus, Tehri Garhwal 249 199, India