title: Excitations of metastable superfluid 4He at pressures up to 40 bars.
abstract: Neutron scattering measurements of the fundamental excitations of liquid 4He confined in 44 A pore diameter gelsil glass at pressures up to 40 bars in the wave vector range 0.4<Q<2.3 A(-1) are reported. Above 25.3 bars and at low temperature (T=0.4 K) the characteristic phonon-roton mode of superfluid 4He is no longer observed as a well-defined mode in the phonon-maxon region (0.4<Q<1.6 A(-1)). Modes at wave vectors Q>1.6 A(-1), especially the rotons, are observed up to complete solidification of all the liquid at a pressure of approximately 40 bars where the roton vanishes. At and above a pressure of 35.1 bars, Bragg peaks are observed, indicating coexistence of liquid and solid in the pores at pressures 35 less than or approximately equal P less than or approximately equal 40 bars.
authors.affiliation: Institut Laue-Langevin, BP 156, 38042 Grenoble, France.
authors.forename: J V
authors.initials: JV
authors.lastname: Pearce
authors.forename: J
authors.initials: J
authors.lastname: Bossy
authors.forename: H
authors.initials: H
authors.lastname: Schober
authors.forename: H R
authors.initials: HR
authors.lastname: Glyde
authors.forename: D R
authors.initials: DR
authors.lastname: Daughton
authors.forename: And N
authors.initials: AN
authors.lastname: Mulders