[1] Univ Blaise Pascal, CNRS, LASMEA, F-63177 Clermont Ferrand, France
[2] RAS, AM Prokhorov Gen Phys Inst, Moscow 117901, Russia
[3] Univ Brasilia, ICCMP, BR-70904970 Brasilia, DF, Brazil
[4] RAS, Inst Solid State Phys, Moscow 117901, Russia
[5] Univ Nacl Autonoma Mexico, Ctr Invest Energia, Temixco 62580, Morelos, Mexico
[6] Univ Southampton, Sch Phys & Astron, Southampton SO17 1BJ, Hants, England
[7] Univ Roma Tor Vergata, Fac Phys, I-00133 Rome, Italy