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.     

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.     

Pressure dependence of size effects in superfluid 4He

We show that the depression of the fourth sound velocity due to size effects over the range 1.4 ? T ? 1.8 K and 0 ? P ? 25 bar can be represented by a function of the displacement thickness δ of Roberts et al. A simple phenomenological model yields values of the healing length which agree with δ within a normalization constant.     

Pulsed-ion study of ultrasonically generated turbulence in superfluid 4He

A pulsed-ion method is used to investigate the turbulent field generated by a beam of ultrasound. Basic information about how ions interact with the vortex tangle is obtained. Global line-density profiles which show how the turbulence convects away from the excited region are also presented.     

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.     

The superfluid fraction near Tλ in dilute solutions of 3He in 4He

Existing second-sound velocity measurements are interpreted to imply an unexpectedly strong concentration dependence for the amplitude of $\text{?}{}_{\mathrm{s}}\text{?}$.     

Spin waves in anisotropic superfluid 3He

Spin waves in the A phase of the superfluid ³He are studied within a microscopic model. It is shown that the spin wave mode with a phonon like dispersion and a gap exists through out the A phase.     

Thermodynamics of textures in superfluid 3He

The contribution of the textures in the B-phase of superfluid ³He to the specific heat has been calculated. The specific heat is found to be divergent near T_c.     

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.     

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.     

The quasiclassical approach to superfluid 3He

We develop the quasiclassical theory for normal and superfluid liquid ³He using a systematic expansion in small parameters such as δ/E_F, ?₀^?1/k_F, etc., and paying particular attention to the high-energy renormalizations of the external pertubations and observables. We apply the general formalism to a number of more specific problems including the derivation of the non-linear quantum kinetic equation for normal ³He, the weak-coupling and strong-coupling free energies and static response functions for superfluid ³He, and the low-frequency and high-frequency dynamics of the superfluid phases. We also discuss extensions of the quasiclassical framework to cover strong short-ranged pertubations such as walls and ions, review recent phenomenological models for the quasiparticle scattering amplitude, and present a brief but self-contained derivation of the Keldysh perturbation theory for real-time Green's functions.     

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.     

Pulsed NMR frequency shifts in superfluid 3He

We report the first measurements of the NMR frequency in ³He A and B under conditions where the net magnetization, M, is tipped far from its equilibrium direction along H_O. In ³He A the frequency shift ω - γH_O varies from the continuous wave value at tipping angle Φ = 0 to a negative shift at Φ = 180°. In ³He B no frequency shift is observed, however for Φ ? 100° a beat pattern is seen to develop in the free induction decay envelope.     

Transverse zero sound propagation in superfluid 3He

Transverse zero sound should propagate in superfluid ³He only in a rather narrow range below T_c.     

The superfluid transition temperature of liquid 3He

The superfluid transition temperature, T_c, is calculated from a scattering amplitude (constructed from the polarization potentials of Aldrich and Pines) which has been shown to yield agreement with experiment for transport properties. Our calculated values agree with experiment at all pressures up to 34 atm.     

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.     

Isoscalar excitations of 24Mg by inelastic 3He scattering

The implications of a rotational model for ²⁴Mg are tested by inelastic ³He scattering to almost all the known states below 11.5 MeV. Multiple excitation calculations are compared to the data for members of known or suspected rotational bands, particularly the 5^? and 6⁺ states. Three examples of 0⁺ excited states are studied, and a very strong excitation of the T = 0 1^? state at 8.438 is found.     

3He(4He)与H2分子碰撞的同位素效应研究

用公认精确度较高的密耦近似方法计算了入射能量E=05eV时惰性气体原子³He(⁴He)与H₂分子替代碰撞体系的转动激发碰撞截面.通过分析³He(⁴He)-H₂碰撞体系分波截面和微分截面的差异,总结出在氦原子的同位素替代情形下³He(⁴He)-H₂碰撞体系分波截面和微分截面随分波数增加和同位素原子质量改变的变化规律. 关键词： 散射截面 密耦方法 同位素替代 散射角     

Hydrodynamic parameters and correlation functions of superfluid 3He

In this paper we present the first of two closely related studies devoted to the connection between the phenomenological hydrodynamics and microscopic theories of superfluid ³He. In this first part, we express in a systematical way all the phenomenological parameters appearing in the hydrodynamic equations in terms of microscopically well defined correlation functions. The method used for this purpose goes back to the work of Kadanoff and Martin on normal fluids and has recently been formulated in the framework of Mori's projector formalism by Forster. Apart from the assumptions about the structure of the superfluid phases of ³He and certain regularity assumptions about the collision-dominated part of the correlation functions, which have to be satisfied if the hydrodynamic limit exists at all, but which remain unproven, this part of our work is nearly exact. The only approximation made is the perturbative treatment of the very small magnetic dipole energy. The k → O limit of various correlation functions is considered. Novel consequences of the directional long range order for the transverse momentum density correlation function of the A phase, which are unique to that phase, are obtained. The instantaneous reactive parameters of the system are expressed as equal time commutators and evaluated rigorously. Some reactive parameters, e.g. the one leading to “orbit waves” are shown to have a collisional part, which has not yet been evaluated in a microscopic theory. NMR is considered as the k → O limit of spin wave resonances with an energy gap due to the magnetic dipole-dipole interaction at k = 0. The NMR linewidth is thereby fixed by the same transport parameter, which determines the spin wave damping in the theory where the gap is neglected. The relevant transport parameter is expressed along with all others by the rigorous Kubo formulae of the theory in which the magnetic dipole energy is neglected. The close analogy of the NMR linewidth parameter to transport parameters like the shear viscosity, which are measured in quite different experiments, is thereby elucidated. Further, approximate evaluations of the Kubo relations of these parameters, within a common microscopic approach will be given in a second related study.     

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.