Ground state surface tension of liquid 3He

A new method for the energy of the fermion liquid in correlated basis function approximation is described. The method is applied to ³He, and extended to a successful variational calculation of the surface tension.     

Observation of a maximum roton velocity in superfluid 4He

Using heat pulses, we detect atoms “evaporated” by ballistic rotons at the free liquid surface. A maximum roton velocity of 160 ± 10ms^?1 is observed.     

Ground state condensate fraction of liquid 4He

An optimal Jastrow correlation function with intermediate- and long-range structure gives a larger condensate fraction at equilibrium density than a simple short-range correlation function. The condensate fraction is also sensitive to the potentials used in the calculation.     

Adsorption on a solid surface dilute liquid mixtures of 4He in 3He at low temperature

Numerical calculations show the ⁴He adsorption near the walls. Superfluid film observations can then be explained by a surface separation.     

Spectrum of 3He atoms in superfluid 4He

It is suggested that at a wave vector near the inverse average interparticle separation, the spectrum of a ³He atom in superfluid ⁴He has a roton like dip. The results of light scattering and transport measurements in liquid ³He-⁴He mixtures can thereby be reconciled.     

Superfluidity of 3He in dilute solutions of 3He in liquid 4He

The possibility of superfluidity of ³He in dilute solutions of ³He in liquid ⁴He is investigated, and the corresponding critical temperature is estimated. The results indicate S-state pairing, i.e., for small concentrations of ³He, the highest transition temperature is obtained for L = 0, but the obtained critical temperatures are very low.     

Astrophysical S factors of radiative 3He4He, 3H4He, and 2H4He capture

The possibility of describing the astrophysical S factors for radiative ³He⁴He capture at energies of up to 15 keV and radiative ³H⁴He and ²H⁴He capture at energies of up 5 keV is considered on the basis of the potential cluster model involving forbidden states.     

On the superfluidity of 3He in dilute mixtures of 3He4He

It is shown on the basis of the experimental data on thermodynamic and transport properties under pressure that the temperatures of the transition of ³He to the superfluid state for ³He-⁴He solutions with concentrations 0.6-3% lie in the range 0.4–1.4 mK.     

Elastic electron scattering from 3He and 4He

The cross sections for elastic electron scattering from ³He and ⁴He were measured for the momentum transfer range from 0.45–2.0 fm^?1. The cross sections were separated into their longitudinal (charge) and transverse (magnetic) contributions using the Rosenbluth formula. The charge and magnetic form factors were obtained model-independently.The rms charge radii were found to be 1.671 (14) fm for ⁴He and 1.976 (15) fm for ³He, and the magnetic rms radius of ³He is 1.99 (6) fm. The mis charge radius for ⁴He is in excellent agreement with the latest muonic data.Comparison of the form factors was made with Faddeev three-body calculations using realistic two-body NN interactions. At present the theoretical calculation is not able to reproduce the experimental data.     

Normalization of the p-3H and n-3He tails of 4He and the 4He charge from factor

It is known that suitable Eckart parametrizations of the nucleon-trinucleo n overlap functions are able to reproduce the charge form factor of ⁴He. The extracted relative normalization constants of the asymptotic nucleon functions are C_n ≈ 4.1 and C_p ≈ 4.0.     

Bose spectrum of superfluid solutions 3He4He

The Bose spectrum of superfluid solutions ³He⁴He is investigated in the case of p-pairing of Fermi particles. Both three-dimensional and two-dimensional models are considered. It is shown that the Bose-Fermi interaction changes the sound velocities in both subsystems. The other collective modes (17 in the 3D-model and 11 in the 2D-model) remain almost unchanged.     

Bound states of 4He

The energies of the bound 0⁺ states of the α-particle are calculated on the basis of four body integral equations with separable ¹S₀ and ³S₁ pair interactions. We find the ground state at z₁ = ?45.73 MeV and an excited o⁺ level is found to be ?11.69 MeV.     

Lifetime of electrons on the liquid surface of superfluid 4He

The lifetime of electrons deposited on the liquid surface of ⁴He was measured. It is smaller than 8 μs at 0.5 K and, as is concluded from its temperature dependence, governed by the electronic mobility parallel to the superfluid surface.     

Cooling dilute 3He4He mixtures to 0.6 mK

We have cooled a ³He⁴He solution to the lowest temperatures yet achieved, 0.58 mK, and find no evidence for a superfluid transition in the dissolved ³He. We have measured the thermal boundary resistance between this solution and sintered 700 Å silver powder, and find that R is proportional to T^?2 between 0.8 mK and 4 mK.     

The elastic scattering of 3He on 4He at medium energies

The differential cross section of the elastic scattering ³He(⁴He, ⁴He)³He has been measured at center of mass energies E_c.m. between 28 and 44 MeV and in the c.m. angular range of 20° to 160°. The ³He polarization P at E_c.m. = 42 MeV and θ_c.m. = 132° was determined in a double scattering experiment. The analysis of the cross section data with the optical and the cluster model has been described previously. The phase shifts obtained in the cluster model calculations were used as starting values in a phase shift analysis. The resulting final real phase shifts and elasticity parameters give good fits to the cross section data. At 44 MeV the elasticity parameters show a pronounced odd-even dependence on angular momentum which had been found already in the case of the real phase shifts. The result of the polarization experiment |P| < 0.22 is consistent with cluster model predictions.     

Ions at the critical interface of 3He4He mixtures

Trapping of ions at the interface of ³He⁴He mixtures has been studied near the tricritical point. The “soft” critical interface leads to a strong dependence of the trapping times both on temperature and on the applied electric field.     

Doppler-shift of fourth sound in flowing 3He4He mixtures

The Doppler-shift Δu₄ of fourth sound propagating in flowing superfluid ³He⁴He mixtures is calculated for arbitrary ³He concentration c. For c ? 0.15 and at T ? 1.4 K a cancellation of the dominant terms in the equation for Δu₄ results in a concentration independent shift.     

Pair condensation of liquid 4He

Particles with equal and opposite momenta are strongly correlated in the ground state of a Bose fluid. An expression is presented which permits practical evaluation of the pairing function describing this coherent effect.     

Anomalous nuclear spin relaxation in liquid 3He4He mixtures

The longitudinal relaxation time, T₁, was measured in liquid ³He⁴He mixtures with molar concentrations of ³He of 0.12, 0.20 and 0.45 under saturated vapor pressure. λ-anomaly was clearly observed in the temperature dependence of T₁.