Related papers: Thermal compression of atomic hydrogen on helium s…
Helium is recognized as a model system for the study of phase transitions. Of particular interest is the superfluid phase in two dimensions. We report measurements on superfluid helium films adsorbed on the surface of a suspended carbon…
Using helium-3 atom scattering, we have studied the adsorption kinetics, the structure and the diffusional dynamics of atomic hydrogen on the surface of a graphene monolayer on Ni(111). Diffraction measurements reveal a 4$^\circ$ rotated…
We have developed a method to probe the temperature of surface state electrons (SSE) above a superfluid Helium-4 surface using the Seebeck effect. In contrast to previously used SSE thermometry, this technique does not require detailed…
We investigated the behavior of H$_2$, main constituent of the gas phase in dense clouds, after collision with amorphous solid water (ASW) surfaces, one of the most abundant chemical species of interstellar ices. We developed a general…
We describe measurements demonstrating laser cooling of an atomic gas by means of collisional redistribution of radiation. The experiment uses rubidium atoms in the presence of several hundred bar of argon buffer gas pressure. Frequent…
We present first experimental data on the high energy behavior of helium atoms quantum reflecting from the nanoscopically disordered surface of a quartz crystal. The use of the light, stable and inert He atom not only opens the unique…
We report a combined experimental and theoretical study of collision-induced dipolar relaxation in a cold spin-polarized gas of atomic nitrogen (N). We use buffer gas cooling to create trapped samples of 14N and 15N atoms with densities…
We present a path-integral Monte Carlo study of dissociation in dense hydrogen ($1.75 \leq r_s \leq 2.2$, with $r_s$ the Wigner sphere radius). As temperature is lowered from $10^5$ to 5000 K, a molecular hydrogen gas forms spontaneously…
We have measured the reduced absorption coefficients occurring in the wings of the potassium 4S-5P doublet lines at 404.414 nm and at 404.720 nm broadened by helium gas at pressures of several hundred Torr. At the experimental temperature…
In these torsional oscillator experiments the samples of solid $^4$He were characterized by measuring their thermal conducitvity. Polycrystalline samples of helium of either high isotopic purity or natural concentration of $^3$He were grown…
We report preliminary heat capacity and vapor pressure measurements of the first and second layers of 4He adsorbed on ZYX graphite. ZYX is known to have much better crystallinity than Grafoil, the most commonly-used exfoliated graphite…
We employ spin-dependent optical dipole forces to characterize the transverse center-of-mass (COM) motional mode of a two-dimensional Wigner crystal of hundreds of $^9$Be$^+$. By comparing the measured spin dephasing produced by the…
We have performed thermal expansion and compressibility measurements on the recently discovered superconducting material NaxCoO2*4xD2O (x=1/3) using neutron powder diffraction over the temperature range 10-295 K and the pressure range 0-0.6…
We developed a highly hydrogen-sensitive thermal desorption spectroscopy (HHS-TDS) system to detect and quantitatively analyze low hydrogen concentrations in thin films. The system was connected to an in situ sample-transfer chamber system,…
High-precision hydrogen spectroscopy is an active field which helps to determine the Rydberg constant and proton charge radius, tests bound-state QED, and can search for Beyond Standard Model (BSM) Physics. Additionally, with recent…
We present an experimental study of electron spin waves in atomic hydrogen gas compressed to high densities of $\sim 5 \times 10^{18}$ cm$^{-3}$ at temperatures ranging from 0.26 to 0.6 K in strong magnetic field of 4.6 T. Hydrogen gas is…
Under a pressure of ~150 GPa solid molecular hydrogen undergoes a phase transition accompanied by a dramatic rise in infra-red absorption in the vibron frequency range. We use the Berry's phase approach to calculate the electric…
Phase transitions, as the condensation of a gas to a liquid, are often revealed by a discontinuous behavior of thermodynamic quantities. For liquid Helium, for example, a divergence of the specific heat signals the transition from the…
The compression of arsenolite (cubic As2O3) has been studied from a joint experimental and theoretical point of view. Experimental X-ray diffraction and Raman scattering measurements of this molecular solid at high pressures with different…
Amorphous hydrogenated silicon (a-Si:H) is an important material for surface defect passivation of photovoltaic silicon (Si) wafers in order to reduce their recombination losses. The material is however unstable with regards to hydrogen (H)…