A.K. Basak

The j-dependence of (3He, d) and (3He, α) reaction analysing powers in the 1p shell

One of the most important experimental results from polarized deuteron studies is the ability to obtain reliable spectroscopic information from measurements of the vector analysin power in transfer reactions. With the availability of a polarized He beam it is of consid- erable interest to determine whether a similar j-dependence of the 3He analysing power exists. Cross section measurements in the 30 MeV region have shown that the (3He,d) and (3He,α) reactions can be quantitatively described by direct reaction theories. Therefore, j-dependence could provide a spectroscopic tool perhaps even more powerful than in reactions with polarized deuterons.

Polarization effects in the elastic scattering of 3He and (3He, d) reaction on 58Ni

Abstract Angular distribution of analysing power of the elastic scattering of 3 He by 58 Ni and analysing power of the 58 Ni( 3 He, d) 59 Cu reaction leading to four excited states of 59 Cu were measured at 33.3 MeV using a polarized 3 He beam. The elastic scattering has been successfully described by phenomenological and “folding” optical-model calculations. The spin-orbit potential was found to be characterized by a small diffuseness parameter between 0.2 and 0.3 fm and strength around 4 MeV. The analysing power of the ( 3 He, d) reaction exhibits a strong j -dependence which is correctly predicted by the distorted wave theory using a 3 He potential determined from the elastic-scattering measurements.

Interactions of polarized 3He particles with 24Mg

Abstract Differential cross sections and analysing powers have been measured for the elastic and inelastic scattering of 33.3 MeV polarized 3He particles by 24Mg and simultaneously for the (3He, d) and (3He, α) reactions leading to the g.s. ( 5 2 + ), 0.451 MeV ( 1 2 + ) and 0.945 MeV ( 3 2 + ) states of 25Al and to the g.s. ( 3 2 + ), 0.451 MeV ( 5 2 + ) and 2.05 MeV ( 7 2 + ) states of 23Mg. The obtained results are compared with the optical model, DWBA, coupled-channels and coupled reaction channels calculations.

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

Abstract The tensor analysing power of the 27 Al(d, 3 He) 26 Mg 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 3 He wave function. The magnitude of the tensor analysing power provides information on the asymptotic D-state to S-state ratio in the 3 He wave function. The value obtained for 3 He is in agreement with the corresponding value for 3 H.

Tensor analysing powers in deuteron elastic scattering by 50Cr, 66Zn and 67Zn

Abstract Vector and tensor analysing powers were measured in deuteron elastic scattering on 50Cr, 66Zn and 67Zn at 12.4 MeV incident deuteron energy. High-accuracy data for T22 show a characteristic dip at ≈ 30° (c.m.) observed on all three nuclei. A phenomenological optical-model analysis has reproduced this feature when a tensor term tR, treated exactly by the programme, was present in the optical potential. Comparable fits to the data have been achieved when the spin-dependent terms of the potential were derived from the deuteron folding model. It is suggested that the deuteron D-state is responsible for the observed behaviour of T22 in elastic scattering at forward angles.

The elastic and inelastic scattering of 33 MeV polarized 3He from oxygen and iron isotopes

Abstract Angular distributions of differential cross sections and analysing powers have been measured for elastic and inelastic scattering of polarized 33 MeV 3 He from 17 O, 18 O, 54 Fe and 56 Fe targets. The elastic data have been analysed to deduce the optical model parameters. The inelastic scattering together with the elastic scattering have been interpreted in terms of a macroscopic model within a coupled-channels framework. From this analysis the deformation parameters, β, were deduced.

Tensor analysing powers of (d, p) reactions on 28Si, 67Zn, 90Zr and 208Pb at 12.3 MeV

Abstract The tensor analysing powers T 20 and T 22 of(d, p) reactions leading to several states of the final nuclei 29 Si, 68 Zn, 91 Zr and 209 Pb were measured at 12.3 MeV deuteron beam energy. The measured tensor analysing powers together with the vector analysing power and cross-section data are compared with DWBA calculations with and without the deuteron D-state. The D-state effects and j -dependence of the tensor analysing powers are discussed. The spin transfers involved in populating the 1.08, 1.88 and 3.30 MeV states in 68 Zn in the 67 Zn(d, p) 68 Zn reaction are deduced to be predominantly 1 2 − . This implies an assignment for the 3.287 MeV level of 68 Zn of J π = 2 + .

Scattering of 33 MeV polarized 3He particles by hydrogen and helium isotopes

Angular distributions of the 3He polarization analysing power were measured for elastic scattering of a 33 MeV polarized 3He beam by 4He, 3He, 3H, 2H and 1H targets. The analysing power data together with the differential cross sections were successfully interpreted in terms of a standard optical model. Two discrete sets of parameters were found for each nucleus. Some features of the optical-model phase-shifts are discussed and compared with other results.

Analysing powers of the 54Fe(He,d)55Co and 54Fe(3He, α)53Fe reactions

Abstract The differential cross sections and analysing powers of the 54 Fe( 3 He, d) 55 Co and 54 Fe( 3 He, α) 53 Fe reactions were measured for strong transitions populating both T and T > states of the final nuclei using a 33 MeV polarized 3 He beam. The sensitivity of the analysing powers to the total angular momentum transfer allowed model-independent determination of spins for all levels observed. The main features of the experimental data could be reproduced satisfactorily by the DWBA formalism only with certain combinations of the optical-model potentials. The analysing power of the indirect transition, when compared with coupled-reaction calculations, show a marked sensitivity to the reaction mechanism.

Scattering and charge-exchange reactions with polarized 3He on lithium isotopes

Abstract Angular distributions of differential cross sections and analysing powers have been measured for elastic and inelastic scattering as well as the charge-exchange reactions induced by 33.3 MeV 3 He on 6.7 Li. The elastic data have been analysed to deduce the optical-model parameters. The inelastic scattering and charge-exchange reactions have been analysed in terms of both macroscopic and microscopic models. A combination of direct and multi-step processes was required to fit the data. The experimental analysing powers were used to distinguish between various reaction mechanisms.