Proton pick-up from Mo

The reaction ⁹²Mo(t, α)⁹¹Nb has been carried out at a triton bombarding energy of 12 MeV. Angular distributions of the emitted α-particles were obtained and compared with DWBA predictions. Relative spectroscopic factors were obtained for six low-lying states and are discussed with reference to shell-model calculations.     

Proton shell structure of mass 28–32 nuclei

Energy spectra of³He-particles from the (d,³He) reaction on^{28, 29, 30}Si,³¹P and³²S have been measured at an incident energy of 52 MeV. Spectroscopic factors have been determined by comparison of measured and DWBA angular distributions. The results are compared with predictions of recent shell model calculations. Excitation energies and spectroscopic strengths of low lying positive parity states are fairly well described. The 1d _5/2 hole strengths distributions are not reproduced. The measured 1p hole strength decreases rapidly from²⁸Si to²⁸S. The occupation numbers of the different subshells show a considerably smoothed Fermi surface of these nuclei.     

One-pion exchange currents effect on the allowed beta-decays in the 1p shell nuclei

A calculation is performed of theft- values for beta-decay allowed transitions in theA=6 ?14 nuclei. The 1p-shell model and the one-pion exchange model are used. It is found that the mesonic corrections are state dependent and may take large values when logft>4.0.     

Spin dipole excitations in radiative pion capture on 1p shell nuclei

Shell-model calculations for spin-dipole transitions in the (π^?,γ) reaction on ^6,7Li, ⁹Be, ¹¹B, ¹³C and ¹⁴N are compared with experimental data. The gross structure of resonance is discussed in terms of configurational splitting and symmetry considerations. Quantum numbers of resonances, total and partial yields are considered. Selected (π^?, γn) and (gp^?, γnγ′) coincidence experiments are proposed. The role of quadrupole and quasielastic excitation is also briefly discussed.     

Proton scattering from unstable nuclei

Recent improvements in the intensities and optical qualities of radioactive beams have made possible the study of elastic and inelastic proton scattering on unstable nuclei. The design and performances of an innovative silicon strip detector array devoted to such experiments are described. The quality of the data obtained are illustrated with recent results obtained at the GANIL facility for unstable oxygen, sulfur and argon isotopes. Methods to analyse the data using phenomenological and microscopic optical model potentials are discussed.     

Excitation of magnetic dipole states in 1p shell nuclei in radiative pion capture

The systematics of magnetic dipole resonance excitation in radiative pion capture on 1p shell nuclei with A = 6–14 is discussed in terms of the shell model with intermediate coupling. Comparison with the electromagnetic transitions is given.     

Triaxial deformation in the 1p shell

Triaxial deformation is found to be important in ¹⁰Be. It lowers the ground-state energy and explains, with a reasonable spin-orbit strength, the strong E₂-transition from the first excited state.     

Spin-tensor decomposition of effective interactions for 0p shell nuclei

The spin-tensor decomposition of effective interactions is carried out in the 0p shell region. As effective interactions, we adopt two different types: one is the Cohen-Kurath interaction and the other is the Hauge-Maripuu interaction. Non-central components of these interactions have natures different to each other. Moreover, it is shown that different kinds of mechanism for determining the energy levels occur in the Cohen-Kurath and Hauge-Maripuu calculations.     

Are there low-lying,intrashell-excited,highly deformed states in the 1f-2p shell nuclei?

It is shown that the improved effective interactions in the fp shell imply the existence of an excited band of states which is much more deformed than the ground state band for some fp shell nuclei. Such states are to a certain extent analogous to the fission isomers occurring in heavy nuclei. Their experimental identification would be interesting and might also help to further improve the effective interaction.     

Inclusive radiative pion capture by N = Z nuclei in the 1p shell

A study of inclusive radiative pion capture by means of sum rules is given for the case of self-conjugated nuclei in the 1p shell. The sum rules M₀ and M₁ are evaluated for the dominant Kroll-Rudermann term in the effective hamiltonian. Total branching ratios and mean photon energies are determined from the calculated sum rules. These quantities compare reasonably well with experiment.     

Total muon capture rates for N = Z nuclei in the 1p shell

The approach to total muon capture rates by means of sum rule techniques is applied systematically to 1p shell nuclei. Explicit calculations involve ground-state wave functions extracted from Cohen-Kurath effective interactions. For the double commutator expectation value we use a form of the potential consistent with the effective interaction and the giant dipole resonance energy.Results are given for N = Z nuclei, studying the minimal sensitivity with the parameter of the improved closure approach. The manifestations of SU(4) breaking are quantitatively shown. Within the uncertainties of the model the rates thus obtained compare reasonably well with experiment.     

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.     

Study of some two-nucleon pick-up reactions in the 1p shell with 39.8 MeV protons

Differential cross sections at a proton energy of 39.8 MeV (lab) have been measured for the following reactions (energies in MeV): ¹²C(p,τ)¹⁰B(g.s., 0.72, 1.74, 2.15, 3.59), ¹⁴C(p, t)¹²C(g.s., 4.43), ¹⁴N(p, τ)¹²C(g.s., 4.43), and ¹⁶O(p,τ)¹⁴N(g.s., 2.31, 3.95). A zero-range DWBA analysis of the data has been performed using the 1p shell wave functions of Cohen and Kurath. The fits we find are overall somewhat worse in shape than those found in the (p, t) survey of the 1p shell performed by Kahana and Kurath, the principal reason being that of the (p, τ) transitions which proceed with both L = 0 and L = 2 components we find several which occur with a much weaker L = 0 strength than the calculations predict. When ratios of experimental integrated cross sections to DWBA integrated cross sections are compared for all transitions, an rms deviation about the mean of 39% of the mean is found, whereas if only ratios for transitions from a given target nucleus are compared, then the rms deviations are considerably smaller.     

Sum rule approach to radiative pion capture: A full hamiltonian calculation for 1p shell nuclei

A sum-rule approach to radiative pion capture is given for the self-conjugated nuclei in the 1p shell. The non-energy-weighted and the energy-weighted sum rules are evaluated for the full effective hamiltonian. Total branching ratios and mean photon energies are determined from these sum rules. A comparison with the Kroll-Rudermann approximation shows that the mean photon energies are practically unaffected, while the total branching ratios increases of the order of 10%.     

Proton halos in exotic light nuclei

The current study on proton halos in exotic light nuclei is reviewed and discussed. We place emphasis on the newly discovered proton halo in ²³Al. A measurement of the reaction cross section of N=10 isotones and Z=13 isotopes is performed at Lanzhou in China. An abnormal increase in the reaction cross section is observed for ²³Al. This abnormal increase, combined with other data, strongly suggests that there is a proton halo in ²³Al. The possible cause for a proton halo in ²³Al is analyzed, and it is found that deformation can be important for it. Other candidates for proton halos are predicted.     

1 states and the 1f-2p shell model

The observed 1⁺ cross sections from (³He, p) reactions on even Ca, Ti, Cr and Fe targets are analyzed in terms of an approximate sum rule. It is shown that the summed 1⁺ cross sections in a qualitative way depend on the proton and neutron number of the target as predicted from the shell model.     

Effect of the shell structure of nuclei on p 15C and p 15N scattering within diffraction theory

The differential cross sections for elastic proton scattering on ¹⁵C and ¹⁵N nuclei at energies of 150 and 800 MeV were calculated within the diffraction theory of Glauber multiple scattering. Shellmodel wave functions were used in these calculations, and particular attention was given to analyzing the sensitivity of the calculated features to distinctions between the shell structure of the ¹⁵C nucleus and the shell structure of the ¹⁵N nucleus. The calculations were performed in the approximation of double scattering. The multiple-scattering operator was written in a form that permits taking into account collisions with nucleons belonging to different shells. It is shown that the difference in structure between the two nuclei in question leads to substantial distinctions between the differential cross sections for scattering at an energy of 800 MeV and scattering angles larger than 25°.     

Optical model analysis of the elastic scattering of 45 MeV 3He particles on 1p shell nuclei

Angular distributions of elastically scattered ³He particles from the 1p shell nuclei ⁶Li, ⁷Li, ⁹Be, ¹⁰B, ¹¹B, ¹²C and ¹⁶O were measured by using a 45 MeV ³He beam. The absolute differential cross section data obtained were analysed in terms of the standard optical model. Using the fact that the rms radius of the 1p shell nuclei is nearly constant a simple folding model allows finding an optical potential family whose real potential depth varies linearly with the target mass. The best fits exhibit a normalized volume integral of about 400 MeV · fm³ for the real potential. From the best-fit parameters a mean parameter set is deduced which varies smoothly with the target mass A_T. The average parameter set compares well with the systematics found for heavier nuclei.