1. “Ilie Murgulescu” Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest, Romania
2. National Institute of Materials Physics, Atomistilor 105bis, 77125 Magurele, Ilfov, Romania
3. National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, 077125 Bucharest, Romania