1. Department of Physics & Astronomy, Trent University, 1600 West Bank Drive, Peterborough, Ontario K9L 0G2, Canada
2. School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
3. Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow 108840, Russia
4. Lebedev Physics Institute, Russian Academy of Sciences, Moscow 117924, Russia
5. School of Electrical and Data Engineering, University of Technology Sydney, Ultimo, New South Wales 2007, Australia