1. International Scientific-Education Center of National Academy of Sciences, M. Baghramyan ave. 24d, 0019 Yerevan, Armenia; Institute of Applied Problems of Physics of National Academy of Sciences, Hr. Nersessian str. 25, 0014 Yerevan, Armenia; and Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, Haus 25, 14476 Potsdam (Golm), Germany