title: Insulator-to-conducting transition in dense fluid helium.
abstract: By combining diamond-anvil-cell and laser-driven shock wave techniques, we produced dense He samples up to 1.5 g/cm(3) at temperatures reaching 60 kK. Optical measurements of reflectivity and temperature show that electronic conduction in He at these conditions is temperature-activated (semiconducting). A fit to the data suggests that the mobility gap closes with increasing density, and that hot dense He becomes metallic above approximately 1.9 g/cm(3). These data provide a benchmark to test models that describe He ionization at conditions found in astrophysical objects, such as cold white dwarf atmospheres.
authors.affiliation: Lawrence Livermore National Laboratory, Post Office Box 808, Livermore, California 94551, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: Celliers
authors.forename: P
authors.initials: P
authors.lastname: Loubeyre
authors.forename: J H
authors.initials: JH
authors.lastname: Eggert
authors.forename: S
authors.initials: S
authors.lastname: Brygoo
authors.forename: R S
authors.initials: RS
authors.lastname: McWilliams
authors.forename: D G
authors.initials: DG
authors.lastname: Hicks
authors.forename: T R
authors.initials: TR
authors.lastname: Boehly
authors.forename: R
authors.initials: R
authors.lastname: Jeanloz
authors.forename: G W
authors.initials: GW
authors.lastname: Collins