Observation of ultrafast nonequilibrium collective dynamics in warm dense hydrogen.
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.
Fäustlin
R R
RR
DESY, Notkestr. 85, 22607 Hamburg, Germany.
Bornath
Th
T
Döppner
T
T
Düsterer
S
S
Förster
E
E
Fortmann
C
C
Glenzer
S H
SH
Göde
S
S
Gregori
G
G
Irsig
R
R
Laarmann
T
T
Lee
H J
HJ
Li
B
B
Meiwes-Broer
K-H
KH
Mithen
J
J
Nagler
B
B
Przystawik
A
A
Redlin
H
H
Redmer
R
R
Reinholz
H
H
Röpke
G
G
Tavella
F
F
Thiele
R
R
Tiggesbäumker
J
J
Toleikis
S
S
Uschmann
I
I
Vinko
S M
SM
Whitcher
T
T
Zastrau
U
U
Ziaja
B
B
Tschentscher
Th
T