3He D-state effects in (d, 3He) reactions

The tensor analysing power of the ²⁷Al(d, ³He)²⁶Mg reaction has been measured at E_d = 12.4 MeV. The results are reproduced by predictions of the DWBA including D-state components in the ³He wave function. The magnitude of the tensor analysing power provides information on the asymptotic D-state to S-state ratio in the ³He wave function. The value obtained for ³He is in agreement with the corresponding value for ³H.     

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.     

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.     

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.     

High temperature spontaneous ferromagnetism and other magnetic phenomena in liquid 3He and 3He4He dilute mixtures

Equilibrium ferromagnetic ordering in liquid ³He at temperatures T ? 0.3 K due to long-wavelength spin fluctuations is predicted. The magnetocaloric effect and other thermodynamic properties of ³He↑ are discussed. The properties of ³He↑⁴He solutions are considered in the case of a restricted geometry.     

Thermal relaxation in liquid 3He/4He mixtures near the tricritical point

Very long relaxation times τ were observed in our earlier specific heat measurements on liquid ³He/⁴He mixtures in two-phase-states near the tricritical temperature T_O. It appear that 1/τ ∝ (T_O ? T).     

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.     

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.     

Odd-even features in 3He + 3H scattering

The single-channel resonating-group method is used to study effects of the Pauli principle on ³He + ³H scattering. Comparison is made with previous similar calculations for d + ³He scattering, and it is found that the Pauli principle affects the s = 0 state of the ³He + ³H system rather similarly to the way it affects the s = 1 state, whereas the Pauli principle affects the $\text{s =}\text{3}\text{2}$ state of the d + ³He system quite differently from the way it affects the $\text{s =}\text{1}\text{2}$ state. Mention is made of the possibility of observing similar effects of the Pauli principle in other nuclear systems.     

Temperature dependence of spin diffusion coefficient and T2 for dilute 3He in solid 4He

Spin diffusion coefficients D and NMR line widths 1/T₂ have been measured as a function of temperature for ³He in solid ⁴He at fractional concentrations down to 10^-4. Minima are seen in D and T₂ and the existence of impuritons is confirmed.     

A study of the 2H(3He, 4He)1H reaction with a polarised 3He beam at 27 and 33 MeV

Angular distributions of the ³He analysing power and differential cross section were measured for the ²H(³He, ⁴He)¹H reaction at incident ³He lab energies of 27 and 33 MeV. Analysis of this and other data suggest the presence of a broad resonance, or resonances, around 28 MeV excitation in ⁵Li. The evidence for the dominant M-matrix elements involving a change in channel spin (i.e. the ΔS = ?1 rule) is examined and also the question is investigated as to whether the data can be consistently explained without requiring tensor forces in the interaction.     

The elastic scattering of polarized 3He by 3He and excitation in the 6Be system

Angular distributions of the polarization in the elastic scattering of ³He by ³He have been measured at eight energies between 18 and 33 MeV, corresponding to excitation of ⁶Be between 20.5 and 28 MeV. The measurements were made using the 33 MeV polarised ³He beam at the University of Birmingham Radial Ridge cyclotron and a small gas target. The data have been analysed in terms of real and complex phase shifts. The deduced phase shift energy dependence cannot be associated with a single isolated level in ⁶Be, however an application of the two-level R-matrix formula reveals some broad L = 3 structures around E_x = 25 MeV.     

This mysterious liquid 3He

The spin contribution to the heat capacity and entropy of ³He has been singled out. With increasing T the spin entropy reaches a constant value, different from ln 2. The spin contribution ≈ ln T can be observed in the temperature dependence of the pressure.     

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.     

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.     

The two-body photodisintegration of the 3He nucleus

The two-body photodisintegration of ³He is calculated using ³He and proton-deuteron wave functions obtained by assuming a separable interaction for the two-nucleon t-matrix. We show that the isotropic component of the cross section is unlikely to yield useful information on the D-state probability densities of the deuteron and ³He. A detailed comparison is made with the data on the cross section at 90°. The separable approximation can account for some of the experimental results, but other experiments suggest that a more sophisticated treatment of the nuclear interactions and wave functions is necessary.     

Effects of exchange and final-state interactions in the reactions 2H(3He, 3H p)p and 2H(3He, 3He p)n

Absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He,³H p)p reactions were measured at E_He = 35.9 MeV. Spectra dominated by the nucleon-nucleon final-state interaction (FSI) are fitted by a fully antisymmetrized PWBA theory which includes the effects of FSI in all its matrix elements. Previously reported 26.8 MeV data showing both FSI and quasi-elastic scattering (both with and without charge exchange) are also fitted by the theory, which qualitatively describes the shapes of all these spectra and the ratios of the cross sections for the various processes. Predictions of Watson-Migdal theory are fitted to the FSI spectra and differences between the two theories are analyzed.     

Initial-state distortion and final-state interactions in the 2H(3He, 3He p)n and 2H(3He, 3H p)p reactions

The predictions of two fully antisymmetrized reaction theories (DWBA and PWBA-FSI) are compared with absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He, ³H p)p reactions exhibiting final-state interactions (FSI) and quasi-elastic scattering (QES) both with and without charge exchange. The DWBA theory takes into account both the initial ³He-d and the final N-N interactions, while the PWBA-FSI theory includes only the latter. New QES data at E_He = 35.9 MeV, as well as previously reported 26.8 and 35.9 MeV data, are fitted. The DWBA theory gives good fits, both in shape and magnitude, to spectra showing N-N final-state interactions but gives somewhat poorer fits to QES spectra whose predicted magnitudes are two to ten times too large. The PWBA-FSI theory always predicts cross sections that are too large; however the predicted shapes are about as good as those from the DWBA. The initial-state interaction is shown to affect both the width and position of QES peaks from these reactions.     

Quasifree processes in the 2H + 3He interaction

Quasifree scattering and quasifree reaction processes have been examined in the ³He+ ²H → p+d+d, ³He + ²H → n+p+³He and ³He+²H → p+p+t reactions. Beam energies of E_d = 22.3 and 35 MeV and of E_3He = 30, 33.5, and 52.5 MeV were used. The experimental results are compared with PWIA calculations and Fourier transforms of the wave functions are extracted. The quasifree processes are described qualitatively by the PWIA, but some features cannot be described by either PWIA or DWIA.