Search

The ( 3 He, d) reaction was studied on all stable Zr isotopes. Twenty-three unbound analog states in the Nb isotopes were populated. The observed cross sections were analyzed using two different methods for DWBA calculations of stripping to unbound analog states. The deduced proton spectroscopic factors are compared to the neutron spectroscopic factors obtained for the parent states from the (d, p) reaction studies. The agreement is generally good, except for the 97 Zr- 97 Nb isotope pair. The difference in the sensitivity to the transferred angular momentum between the (d, p) reaction and the ( 3 He, d) reaction to the analog states is discussed. The good agreement leads us to conclude that the ( 3 He, d) reaction to analog states may be used in nuclear spectroscopy for the study of levels in the parent states which are populated through large angular momentum transfer.

The reactions 95, 97 Mo(p, d) 94, 96 Mo were studied at a proton energy of 26 MeV. Angular distributions were measured from 11° to 40° and compared with distorted-wave Born approximation calculations; l -values and spectroscopic factors were extracted for the low-lying states of 94 Mo and 96 Mo. The angular distributions of these states have a characteristic l = 2 shape. The ratios of the summed spectroscopic factors to the 0 + , 2 + and 4 + states are in good agreement with the (2 d 5 2 ) n neutron configurations. The 2 + strength is strongly fractionated in both 94 Mo and 96 Mo. The 4 + strength in 94 Mo is split among two states, whereas in 96 Mo it is concentrated in the second 4 + state.

The nuclear structure of 50 Sc is investigated through the 48 Ca( 3 He, p) 50 Sc reaction using 3 He ions accelerated to 18.5 MeV in a cyclotron and semiconductor detectors. Data are obtained on the excitation energies and the spins and parities of a large number of levels in 50 Sc up to 6.62 MeV. The experimental data are compared with DWBA calculations using various wave functions obtained in the framework of the shell model with different degrees of sophistication as to the orbits considered. A reasonable agreement is obtained up to 3.5 MeV excitation energy in 50 Sc for the most complex wave functions. Above 3.5 MeV, the results indicate the existence of strong L = 2 transitions in the ( 3 He, p) reaction, which are not explained by current models, and also a new and previously unidentified collective mode of excitation in 50 Sc.

We have studied levels in $^{58}\mathrm{Ni}$ up to 10 MeV excitation energy through the ($\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}$) reaction at 30 MeV and found surprising overall agreement between the observed spectra and those from $\ensuremath{\alpha}$-transfer reactions.

A systematic study of collective states excited in 44 MeV α-particle inelastic scattering by nuclei near closed shells with 28 neutrons, 20, 28, 50 and 82 protons is presented. The nuclei studied are 40Ca, 46, 48, 50Ti, 52Cr, 54, 56, 58Fe 58, 60, 62, 64Ni, 112, 114, 116, 118, 120, 122, 124Sn and 208Pb. The theoretical analysis has been performed with the Austern-Blair model. The deformation lengths and transition probabilities obtained are compared with several experimental and theoretical data. A discussion of the two-phonon states is given.

The doubly odd nuclei 48 Sc, 50 V, 52 Mn and 54 Co have been studied by the charge exchange reaction ( 3 He, t) on 48 Ca, 50 Ti, 52 Cr and 54 Fe enriched targets. In addition to the analogue state of the target ground state, we observed a great number of low-lying energy levels, especially those which can be described by the [( f 7 2 ) p ( f 7 2 ) n −1 ] configuration. For these levels we got angular distributions from 10° to 70° c.m. We observed that these angular distributions show a typical pattern for each value of the total transferred angular momentum J as shown by levels of 48 Sc, 52 Mn and 54 Co for which spins are already known. This property allowed us to propose J -values for the more excited levels. Thus, most of the components of the [( f 7 2 ) p ( f 7 2 ) n −1 ] multiplet have been identified in 48 Sc, 50 V and 52 Mn. For 48 Sc, angular distributions are practically identical at 18.5 and 30.2 MeV. It seems that the ( 3 He, t) reaction at 30.2 MeV on N = 28 targets proceeds through an apparently quite simple mechanism.

ABS>The plausibility of interpreting the inelastic scattering of alpha particles by the odd nuclei Cu/sup 63/ and Cu/sup 65/ in terms of the coupling of a 3/2- proton to the nuclei Ni/sup 62/ and Ni/sup 64/ respectively is examined. It is assumed that there is a non-negligible interaction between the outside proton and the even Ni nucleus. The interpretation is based on a comparison of inelastic alpha scattering by the four nuclei under consideration. (T.F.H.)

Nous avons etudie simultanement les etats de neutron de 55Fe et les etats de proton T> et T< de 55Co. On donne les resultats concernant les principaux niveaux ƒ1/2, p3/2, p1/2, ƒ5/2 et g9/2 avec les facteurs spectroscopiques relatifs tires d'une analyse en ondes deformees.

A study of single-particle proton strengths in odd-mass Tc isotopes was performed using the (3He, d) reaction. Angular distributions were measured from 8° to 70° and compared with calculations using the distorted-wave Born approximation. The l-values and spectroscopic factors were extracted and compared with (d, n) results. Proton configurations for the ground states of 92,94Mo and 96Mo were deduced from the analysis. Symmetry energies were extracted from the energy difference between the centroids of the T> and T< states. Various methods for DWBA calculations for unbound states are discussed.

Single neutron hole states in neutron magic N = 82 nuclei have been investigated using the (p, d) pick-up reaction on 138 Ba, 140 Ce, 142 Nd and 144 Sm with 24.55 MeV protons and about 45 keV overall energy resolution. Energy levels corresponding to the shell-model orbitals 2d 3 2 , 3s 1 2 , 1h 11 2 , 2d 5 2 and 1g 7 2 have been observed in all the residual nuclei. Absolute or relative differential cross sections measured between 15° and 80° in 5° steps have been compared with DWBA calculations. All the excitation spectra investigated show similar features characteristic of pure neutron hole states for the low-lying 3 2 + , 1 2 + and 11 2 − states and of configuration mixing above 1 MeV excitation energy for the 2d 5 2 and 1g 7 2 orbitals. For 144 Sm the polarized proton beam has been used to confirm some spin assignments. Evidence for the neutron-proton interaction effect on the location of the various orbitals is shown.

We describe an experimental study of (α, t), (α,3He) reactions at 44 MeV using a solid-state identifier, on the target nuclei 54Fe and 58, 60, 62, 64Ni. A critical study of optical-model and distorted-wave analysis has been performed. We show the complementarity of different transfer reactions, the ambiguity of the spectroscopic factors and the importance of the problem of the reaction mechanism.

The reactions 203,205 Tl(α, t) 204,206 Pb were investigated at an incident energy of 44 MeV, the reactions products being momentum analysed in a double ΔE + E particle identification system with semiconductor counters. The resulting energy resolution was 120 keV. Transitions were observed to the ground state and the lowest 2 + state of 204,206 Pb and to a number of states at higher excitation energies, starting at about 2.9 MeV in 204 Pb and about 2.6 MeV in 206 Pb. Angular distributions were measured for the triton groups corresponding to the ground and first excited states of 204 Pb. The distributions have a forward peaked shape which can be reproduced well by a DWBA calculation assuming a simple proton stripping process.

The ($sup 3$He,d) reaction on Ni isotopes was studied at 30.2 MeV bombarding energy. Twenty-six unbound analog states in Cu isotopes were populated, and the observed differential cross sections are presented. Two different distorted-wave Born-approximation methods for stripping calculations to unbound analog states were used in the analysis. Proton spectroscopic factors were deduced and compared with published neutron spectroscopic factors for the parent states. The agreement is generally good, except for the pair of isotopes $sup 62$Ni-$sup 62$Cu. The different sensitivity to the transferred angular momentum of the corresponding (d,p) and ($sup 3$He,d) reactions is discussed. The present data are compared with the results of previous studies of the ($sup 3$He,d) reaction in the A approx. 90 mass region. It is concluded again that the ($sup 3$He,d) reaction to analog states is complementary to the (d,p) reaction for the study of levels in the parent states which are populated through large angular momentum transfers. (AIP)

Experimental results obtained at Saclay by alpha-particle scattering have been analysed with the Austern- Blair model. Deformation parameters δ 2 I and transition probabilities B ( I →0) are compared with other experimental data and theoretical predictions.

“Two-phonon” excitations observed at Saclay by alpha-particle scattering have been analysed with the Austern -Blair model. The experimental data are not always in agreement with a “two-phonon” description of those levels.

Angular distribution measurements for elastic and inelastic scattering of 1.04 GeV proton by 12 C, 58 Ni and 208 Pb with an energy resolution of the order of 100 keV are presented.

La diffusion inelastique de particules α de 44,0 ± 0,2 MeV par 48Ti, 58Fe, 62Ni, 64Ni a ete etudiee. L'analyse des distributions angulaires permet de determiner la parite, et quelquefois le spin et le parametre de deformation pour les niveaux a un phonon, et d'obtenir des renseignements sur le comportement des niveaux relevant de la double excitation nucleaire. Ces resultats, joints a ceux obtenus anterieurement, permettent de dresser un tableau general de l'evolution des excitations collectives dans la region 22 ≤ Z ≤ 30.