1. Al.I. Cuza Univ., Department of Physics, Iasi, Romania + Al. I. Cuza Univ., Departament Interdisciplinary Research-RAMTECH center, Iasi, Romania
2. Al.I. Cuza Univ., Department of Physics, Iasi, Romania
3. Polytechnics University of Bucharest, Gh. Polizu, Bucharest, Romania
4. Al.I. Cuza Univ., Iasi, Department of Physics, Romania