1. Department of Inorganic and Organic Chemistry, Biochemistry and Catalysis, Faculty of Chemistry, University of Bucharest, Boulevard Regina Elisabeta Nr. 4-12, 030018 Bucharest, Romania
2. Department of Physics, Universitaty Politehnica of Bucharest, 313 Spl. Independentei, 060042 Bucharest, Romania
3. B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68-2 Niezalezhnastsi Avenue, 220072 Minsk, Belarus