1. Institute
of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock, Germany
2. ExxonMobil Research & Engineering Company, 1545 Route 22 East, LD 152, Annandale, New Jersey 08801, United States
3. Center
for Engineering Sciences, Martin-Luther-University Halle-Wittenberg, 06099 Halle/S., Germany