Shell-model calculations on Ni and Cu isotopes

Binding energies, excitation energies and spectroscopic factors have been calculated for^57–67Ni and^58–68Cu in an unrestricted (2p_3/2, lf _5/2,2p_1/2) shell-model space. The effective two-body matrix elements are obtained from the modified surface delta interaction (MSDI) and from a least-squares fit to experimental binding and excitation energies (ASDI). The average deviation between about 100 experimental and calculated energies is 0.14MeV for MSDI and 0.08 MeV for ASDI. Excitation energies of high-spin states are given also. Spectroscopic factors have been calculated for all single-nucleon transfer reactions on stable Ni or Cu targets leading to Ni or Cu isotopes. For spectroscopic factors larger than 0.4 the average deviation between theory and experiment is about 30%. The experimentally observed and calculated spectroscopic strengths are compared by using sum rules and are found to be consistent. An extensive compilation has been made of experimental data on energies,J ^π assignments and spectroscopic factors.     

High-resolution investigation of the 112Sn(p,p')112Sn reaction

The ¹¹²Sn(p, p') reaction was studied at proton energies of 20.51 and 25.0 MeV. The outgoing protons were momentum analysed with an Enge split-pole spectrograph and recorded with position-sensitive solid-state detectors with a total resolution between 10 and 15 keV. Excitation energies and angular distributions for states below 5.5 MeV excitation energy were obtained. The angular distributions were compared with macroscopic DWBA calculations in order to extract L-values and deformation parameters. Coupled-channels calculations were performed to investigate two-phonon excitations and the mixing between one- and two-phonon states. The results of the present experiment are compared with previous experimental results and with number-projected BCS calculations. The results for some of the excited states were compared with similar results for the other even Sn isotopes.     

High-resolution investigation of the 112Sn(p,d)111Sn reaction

The ¹¹²Sn(p, d)¹¹¹Sn reaction was studied at a proton energy of 27.45 MeV. The outgoing deuterons were momentum analyzed with an Enge split-pole spectrograph and recorded with position-sensitive solid-state detectors with a total resolution between 12 and 16 keV. Angular distributions were compared with DWBA calculations in order to extract l-values, spectroscopic factors, single-quasiparticle energies and occupation probabilities. In the gross structure between 3 and 6 MeV, which was interpreted as being due to the pickup of deeply bound neutrons, several discrete peaks were also found with an angular distribution characteristic for l = 1 or 4 transfer. The excitation of core-coupled states was investigated by performing two-step DWBA calculations. The results of the present experiment are compared with previous experimental results and with number-projected BCS calculations.     

Study of neutron-rich Mo isotopes by the projected shell model approach

The projected shell model (PSM) calculations have been performed for the neutron-rich even–even ^102?110Mo and odd—even ^103?109Mo isotopes. The present calculation reproduces the available experimental data on the yrast bands. In case of even–even nuclei, the structure of yrast bands is analysed and electromagnetic quantities are compared with the available experimental data. The g-factors have been predicted for high spin states. For the odd-neutron nuclei, the structures of yrast positive- and negative-parity bands are analysed and found to be in reasonable agreement with the experiments for ^103?107Mo. The disagreement of the calculated and observed plots for energy staggering quantity clearly establishes the occurrence of sizable triaxiality in ^103,105Mo and also predicts a decrease in the quantum of triaxiality with increasing neutron number and angular momentum for odd mass neutron-rich Mo isotopes.     

Investigation of the neutron shell structure of the even-even isotopes <Superscript>40–56</Superscript>Ca within the dispersive optical model

Within the method of matching experimental data obtained in the neutron-stripping and neutron-pickup reactions on ^{40,42,44,46,48}Ca isotopes, the single-particle energies and probabilities that neutron states are filled are obtained for the even-even calcium isotopes. These data are analyzed within the dispersive optical model, and good agreement between the calculated and experimental values of the energies of states is obtained. The dispersive optical potential is extrapolated to the region of the unstable ^50,52,54,56Ca nuclei. The calculated single-particle energies of bound states in these isotopes are compared with the results of the calculations within the multiparticle shell model, the latter predicting a new magic number N = 34 for Z = 20 nuclei.     

The level structure of 189Os

The level structure of ¹⁸⁹Os has been studied by (d, p), (d, t) and (d, d') reaction spectroscopy at E_d = 12.1 MeV. Assignments of a number of levels at excitation energies below ≈ 1700 keV are given. The assignments are discussed in terms of a unified model based on the Nilsson model including pairing, rotational motion and attenuated Coriolis coupling. Deviations between predicted and experimental excitation energies and wave functions are generally found to be consistent with trends observed in ¹⁸⁷Os and in the odd W isotopes. Evidence for the existence of collective non-rotational states is found from the (d, d') reactions. Results of (³He, α) and high resolution γ-ray and conversion electron studies were also included at various stages of the investigation to supplement the data from the deuteron induced reactions. Comparisons between calculated and measured B(E2) values are found to indicate an intrinsic quadrupole moment of the ground-state band of ≈ 5.0 b, in agreement with values in adjacent even Os isotopes. Details of the Coriolis coupling calculations are given.     

Positive parity states and some electromagnetic transition properties of even-odd europium isotopes

The positive-parity low-spin states of even-odd Europium isotopes (^151–155Eu) were studied within the framework of the interacting boson-fermion model. The calculated positive low-spin state energy spectra of the odd Eu isotope were found to agree quite well with the experimental data. The B(E2) values were also calculated and it was found that the calculated positive-parity low-spin state energy spectra of the odd-A Eu isotopes agree quite well with the experimental data.     

A study of the odd isotopes of copper using the 58, 60, 62, 64Ni(τ, d) 59, 61, 63, 65Cu and 48Ca(τ, d)49Sc reactions

Experimental measurements are reported for the ^{58, 60, 62, 64}Ni(τ, d) ^{59, 61, 63, 65}Cu and ⁴⁸Ca(τ, d)⁴⁹Sc reactions and for the elastic scattering of ³He particles from ^{58, 60, 62, 64}Ni and ⁴⁸Ca targets at an incident energy of 18 MeV. The (τ, d) angular distributions cover the angular range from approximately θ_c.m. = 5° to 90° and the elastic scattering angular distributions range from θ_c.m. = 12° to 172°. In the (τ, d) reactions several weakly excited states, not previously seen in stripping reactions, have been identified and assignments of the transferred angular momentum made. The ⁴⁸Ca(τ, d)⁴⁹Sc reaction data are used in conjunction with the theoretical sum rules of MacFarlane and French to determine the normalization factors to be used with DWBA calculations for different sets of optical potentials. These normalization factors are used to extract spectroscopic strengths and centroid energies from the Ni(τ, d)Cu data which are compared with published model calculations for the odd copper isotopes. It is concluded that these calculations invariably fail to give a consistent picture of the odd copper isotopes mainly due to the use of centroid energies as variable parameters in the model calculations.     

Shell-model calculations for the zinc isotopes

Shell-model calculations for the zinc isotopes have been carried out with active particles distributed in the $\text{1}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{, 0}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{and}\text{1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ orbits outside a closed “⁵⁶Ni” core. The effective Hamiltonian used was one obtained by Koops and Glaudemans from a fit to Ni and Cu level energies. An average absolute deviation of 0.19 MeV between the calculated and experimental ground-state binding energies is obtained for the A = 62?68 Zn isotopes. Good agreement is also found between most calculated and experimental excitation energies and spectroscopic factors for single-nucleon transfer for the low-lying levels in these nuclei. Experimentally known B(E2) values are generally well reproduced by the present model with effective charges of 1.0 ± 0.1 and 1.6 ± 0.2 for the neutron and proton, respectively. Magnetic dipole as well as Gamow-Teller transitions are not well accounted for by these calculations and seem to be sensitive to excitations of the ⁵⁶Ni core.     

Proton spectroscopic factors of Sm isotopes in the pairing-plus-quadrupole model

Proton spectroscopic factors have been calculated for the single-proton states in Sm isotopes with N = 84–92 by using the deformed quasiparticle wave functions obtained in the pairing-plus- quadrupole model. Comparison is given with the experimental data from the pick-up reactions (d, ³He) and (t, ⁴He) to the product nuclei ^145–153Pm. Effects of deformation on the spectroscopic factors are studied.     

Low-lying dipole excitations in the stable Cd isotopes: A systematics

Low-lying dipole excitations in the medium-weight vibrational nuclei of the Cd isotopic chain were investigated by means of nuclear resonance fluorescence experiments performed at the bremsstrahlung beam of the Stuttgart Dynamitron accelerator (endpoint energy 4.1 MeV). Detailed information has been obtained on excitation energies, spins, decay widths, and transition probabilities of numerous excited states in ^{110–114,116}Cd. Additionally, the use of two Compton polarimeters enabled model-independent parity assignments for excitations in the even-even isotopes. Strongly excited J ^π = 1^? states are found in all even-even Cd nuclei at excitation energies near the sumof the energies of the first 2⁺ and 3^? states. These excitations are interpreted as the 1^? member of the quadrupole-octupole coupled quintuplet (2+?3^?). The fragmented strength observed in the odd isotopes ^111,113Cd is compared with the strength distributions in the neighboring even-even Cd isotopes.     

Action d'un champ magnetique sur le taux de polarisation de la raie interdite 2655,6 Å (61S0-63P0) du mercure

The forbidden radiation 2655.6 Å (6¹S₀-6³P₀) emitted by the odd isotopes of mercury is polarized in a magnetic field, even if the atoms are isotropically excited. The degree of polarization has been calculated for the case of ¹⁹⁹Hg. The experimental results agree with the theoretical predictions.     

The influence of correlations on the odd-mass Nuclei21Ne and25Mg

Excitation energies and electromagnetic properties of the low energy spectra of²¹Ne and²⁵Mg have been calculated using the Multi-Configuration-Hartree-Fock (MCHF) model. BothT=0 andT=1 pairing correlations are found to be simultaneously important in those odd mass nuclei. Furthermore, though axial symmetry was requested, quite good agreement with the experimental data is reached.     

FixedJ spectral distributions in large shell model spaces

The centroids and widths defining Gaussian approximate spectroscopic strength distributions ofnJT spaces are calculated exactly via a direct method. The results in the (sd) shell nuclei and even mass Pb isotopes with 198≦A≦204 exhibit a smooth behaviour versusJ of both fixedJT centroids and widths if the spectroscopic space dimensionality is large enough.     

The two-particle-one-hole states in the odd-A antimony isotopes

The two-particle-one-hole states, experimentally observed in the odd-A antimony isotopes are explained in a particle-core coupling model. The wave functions for these states are discussed. Theoretical and experimental spectroscopic factors for a (d,³He) reaction on the double even Te isotopes are compared. Electric quadrupole reduced transition probabilities in¹²¹Sb are discussed.     

Quantum Monte Carlo calculation for the neutron-rich Ca isotopes

We computed ground-state energies of calcium isotopes from ⁴²Ca to ⁴⁸Ca by means of the Auxiliary Field Diffusion Monte Carlo (AFDMC) method. Calculations were performed by replacing the ⁴⁰Ca core with a mean-field self-consistent potential computed using the Skyrme interaction. The energy of the external neutrons is calculated by projecting the ground state from a wave function built with the single-particle orbitals computed in the self-consistent external potential. The shells considered were the 1F _7/2 and the 1F _5/2 . The Hamiltonian employed is semi-realistic and includes tensor, spin-orbit and three-body forces. While absolute binding energies are too deep if compared with experimental data, the differences between the energies for nearly all isotopes are in very good agreement with the experimental data.     

Single-particle properties of <Emphasis Type="Italic">N</Emphasis> = 12 to <Emphasis Type="Italic">N</Emphasis> = 20 silicon isotopes within the dispersive optical model

Experimental neutron and proton single-particle energies in N = 12 to N = 20 silicon isotopes and data on neutron and proton scattering by nuclei of the isotope ²⁸Si are analyzed on the basis of the dispersive optical model. Good agreement with available experimental data was attained. The occupation probabilities calculated for the single-particle states in question suggest a parallel-type filling of the 1d and 2s _1/2 neutron states in the isotopes ^{26,28,30,32,34}Si. The single-particle spectra being considered are indicative of the closure of the Z = 14 proton subshell in the isotopes ^30,32,34Si and the N = 20 neutron shell.     

The role of the imaginary form factor in the microscopic description of (p,p′) scattering from nuclei with one closed shell

The inelastic scattering of protons from the lowest 2⁺ and 3^? levels in ⁴⁰Ca, Ni, Sn and N = 50 isotopes is analyzed for different incident proton energies. The addition of a collective imaginary term to the microscopic real form factor very much improves the agreement between the calculated and experimental cross section angular distributions. The variation with energy of the relative contributions of the ΔT = 1 and gDT = 0 isospin parts of the transitions is discussed.