The principal resolution limitation in electron cryomicroscopy of frozen-hydrated biological samples is radiation damage. It has long been hoped that cooling such samples to just a few kelvins with liquid helium would slow this damage and allow statistically better-defined images to be recorded. A new "G2 Polara" microscope from FEI Company was used to image various biological samples cooled by...

Positively charged ions were produced in supercritical helium at temperatures from 6 to 10 K and up to 2 MPa using a corona discharge. Their mobility was measured via current-voltage curves, and the hydrodynamic radius was derived using Stokes law. An initial increase and subsequent decrease of hydrodynamic radius was observed and interpreted in terms of growth, compression and solidification o...

The specific heat of liquid helium was calculated theoretically in the Landau theory [1]. The results deviate from experimental data in the temperature region of 1.3 2.1 K. Many theorists subsequently improved the results of the Landau theory by applying temperature dependence of the elementary excitation energy [2], [3]. As well known, many-body system has a total energy of Galilean covariant ...

Investigations of two-dimensional electron systems (2DES) have been achieved with two model experimental systems, covering two distinct, non-overlapping regimes of the 2DES phase diagram, namely the quantum liquid phase in semiconducting heterostructures and the classical phases observed in electrons confined above the surface of liquid helium. Multielectron bubbles in liquid helium offer an ex...

The dynamics of the development of instability of the free surface of liquid helium, which is charged by electrons localized above it, is studied. It is shown that, if the charge completely screens the electric field above the surface and its magnitude is much larger then the instability threshold, the asymptotic behavior of the system can be described by the well-known 3D Laplacian growth equa...

Measurements of the specific heat of liquid helium confined in all three spatial dimensions shows an anomalous behavior that suggests a coupling of individual regions of superfluid. This coupling is thought to occur through the shallow channels used to fill the boxes used as confinement structures. This may be evidence of a proximity effect where helium in the larger boxes modifies the behavior...

Abstract We have proposed a model of roton cluster excitations in liquid helium II based on a Schrödingertype equation with a self-consistent confining potential. We have derived an equation for the number of atoms in roton excitations, which can be treated as quantum 3D solitons, depending on vibrational quantum numbers. It is shown that the smallest roton cluster is in the symmetric vibration...

A novel density functional, which accounts correctly for the equation of state, the static response function and the phonon-roton dispersion in bulk liquid helium, is used to predict static and dynamic properties of helium droplets. The static density profile is found to exhibit significant oscillations, which are accompanied by deviations of the evaporation energy from a liquid drop behaviour ...