1. Institute of Theoretical Physics and Astronomy, Faculty of Physics, Vilnius University, LT-10257 Vilnius, Lithuania
2. Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-10691 Stockholm, Sweden
3. Department of Physics, Faculty of Mathematics and Natural Sciences, Kaunas University of Technology, LT-51368 Kaunas, Lithuania