1. Natubhai V. Patel College of Pure & Applied Sciences, The C.V.M. University, Vallabh Vidyanagar 388 120, Gujarat, India
2. Department of Physics, Sardar Patel University, Vallabh Vidyanagar 388 120, Gujarat, India
3. C. L. Patel Institute of Studies and Research in Renewable Energy, The C.V.M. University, Vallabh Vidyanagar 388 129, Gujarat, India