1. Department of Physics, Addis Ababa University, 1176, Addis Ababa, Ethiopia
2. Laser Research Institute at the Department of Physics, Stellenbosch University, 7602, Stellenbosch, South Africa
3. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE412 96, Goteborg, Sweden
4. Department of Chemistry, Addis Ababa University, 33658, Addis Ababa, Ethiopia