1. Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, Moscow 143026, Russia
2. Institute of Spectroscopy, Russian Academy of Sciences, Fizicheskaya 5, Troitsk, Moscow 108840, Russia
3. Phaculty of Physics and International Laser Center, Lomonosov Moscow State University, Moscow 119991, Russia
4. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States