Observation of ultrafast nonequilibrium collective dynamics in warm dense hydrogen

• Published in: Physical review letters 2010-03, Vol.104 (12), p.125002-125002, Article 125002
• Main Authors: Fäustlin, R R, Bornath, Th, Döppner, T, Düsterer, S, Förster, E, Fortmann, C, Glenzer, S H, Göde, S, Gregori, G, Irsig, R, Laarmann, T, Lee, H J, Li, B, Meiwes-Broer, K-H, Mithen, J, Nagler, B, Przystawik, A, Redlin, H, Redmer, R, Reinholz, H, Röpke, G, Tavella, F, Thiele, R, Tiggesbäumker, J, Toleikis, S, Uschmann, I, Vinko, S M, Whitcher, T, Zastrau, U, Ziaja, B, Tschentscher, Th
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATORS; BOSONS; COLLISIONS; CROSS SECTIONS; CYCLIC ACCELERATORS; DATA; DESY; ELECTRON COLLISIONS; ELECTRON DENSITY; ELECTRON TEMPERATURE; ELECTRONS; ELEMENTARY PARTICLES; ELEMENTS; ENERGY RANGE; EV RANGE; EXPERIMENTAL DATA; FERMIONS; FLUIDS; FREE ELECTRON LASERS; HYDROGEN; INELASTIC SCATTERING; INFORMATION; ION TEMPERATURE; IONIZATION; LASERS; LEPTONS; LIQUIDS; MASSLESS PARTICLES; NON-EQUILIBRIUM PLASMA; NONMETALS; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUMERICAL DATA; PHOTONS; PLASMA; SCATTERING; SYNCHROTRONS; THOMSON SCATTERING
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.104.125002

We investigate ultrafast (fs) electron dynamics in a liquid hydrogen sample, isochorically and volumetrically heated to a moderately coupled plasma state. Thomson scattering measurements using 91.8 eV photons from the free-electron laser in Hamburg (FLASH at DESY) show that the hydrogen plasma has been driven to a nonthermal state with an electron temperature of 13 eV and an ion temperature below 0.1 eV, while the free-electron density is 2.8x10{20} cm{-3}. For dense plasmas, our experimental data strongly support a nonequilibrium kinetics model that uses impact ionization cross sections based on classical free-electron collisions.