3He spin diffusion measurements in 3He- 4He mixture films

3He spin diffusion measurements for 3He-4He mixture films on Nuclepore are reported as a function of 3He coverage for 0. 030相似文献   

Heat-capacity studies of (3)He in (3)He-(4)He mixture films and the coverage dependence of the two-dimensional (3)He Landau Fermi-liquid parameters

The heat capacity of (3)He in (3)He-(4)He mixture films on a nuclepore substrate is reported over the temperature range 90相似文献   

Adsorption and two-body recombination of atomic hydrogen on 3He-4He mixture films

We present the first systematic measurement of the binding energy E(a) of hydrogen atoms to the surface of saturated 3He- 4He mixture films at temperatures 70-400 mK. E(a) is found to decrease almost linearly from 1.14(1) K down to 0.39(1) K, when the population of the ground surface state of 3He grows from zero to 6x10(14) cm(-2), yielding the value 1.2(1)x10(-15) K cm(2) for the mean-field parameter of H- 3He interaction in 2D. Measuring by ESR the rate constants K(aa) and K(ab) for second-order recombination of hydrogen atoms in hyperfine states a and b, we find the ratio K(ab)/K(aa) to be independent of the 3He content and to grow with temperature.     

Third sound detection of superfluid transitions in 3He-4He films

Experiments in ³He⁴He films using the torsional oscillator method suggest the existence of two superfluid transitions. We only detect the low temperature superfluid transition T_A by third sound velocity measurement, which raises the question of the existence of percolation between superfluid clusters at T>T_A.     

Determination of the composition of a 3He-4He mixture from the transmission of thermal neutrons

A beam of monochromatic thermal neutrons — wavelength about 1 Å — is used to determine the composition of a mixture of ³He and ⁴He. The method offers a precision ΔX ⩽ 0,01 over the complete concentration range. This is due to the difference in total neutron cross section, the latter is about a thousand times larger for ³He than for ⁴He.     

Enhanced polarization in 3He-4He solutions

It is pointed out that the equilibrium ratio of the nuclear spin polarizations of two ³He systems in contact is proportional to the ratio of their volume susceptibilities and inversely proportional to the ratio of their densities. Hence the polarization of dilute ³He-⁴He solutions can be enhanced by 40% or more over the polarization of pure ³He.     

Dimers in two-dimensional 3He- 4He mixtures

Ground-state properties of two-dimensional 3He- 4He mixtures are studied at zero temperature. A general argument based on the long-ranged attraction of the phonon exchange is given for the existence of 3He dimers in low-concentration mixtures with 4He. The binding energy of dimers ranges from milli- to microkelvins with increasing 4He density. By comparing the 3He impurity chemical potential in 4He with the one in pure 3He we conclude that at finite pressures 3He dimers form a mixture with 4He with a maximum solubility of approximately 3%.     

Nuclear magnetic relaxations times of 3He IN 3He-4He solutions

The longitudinal and transverse relaxation times T₁ and T₂ of the nuclear spins of ³He in solution in ⁴HE for high and low temperatures are calculated and shown to be equal for reasonable external magnetic fields. The result is compared with experimental data.     

Quantized vortices in mixed 3He-4He drops

Using density functional theory, we investigate the structure of mixed (3)He(N3)-(4)He(N4) droplets with an embedded impurity (Xe atom or HCN molecule) which pins a quantized vortex line. We find that the dopant+vortex+(4)He(N4) complex, which in a previous work [F. Dalfovo et al., Phys. Rev. Lett. 85, 1028 (2000)] was found to be energetically stable below a critical size N(cr), is robust against the addition of 3He. While 3He atoms are distributed along the vortex line and on the surface of the 4He drop, the impurity is mostly coated by 4He atoms. Results for N4 = 500 and a number of 3He atoms ranging from 0 to 100 are presented, and the binding energy of the dopant to the vortex line is determined.     

The flow properties of pure 4He and of 3He-4He mixtures at temperatures below the lambda-point

The flow of pure ⁴He and of ³He-⁴He mixtures at temperatures below the lambda-point through a slit with a width of 0.3 micron as a function of hydrostatic pressure heads up to 7000 cm He and fountain pressure differences up to 2500 cm He has been studied. It is concluded that the flow resistance is proportional to the slit length. Values of the normal fluid viscosity, of the normal fluid fraction and of the lambda-point temperature as a function of the ³He-concentration are given. The volume contraction on mixing the two isotopes is estimated.